You are given a text that consists of multiple sentences. Your task is to perform abstractive summarization on this text. Use your understanding of the content to express the main ideas and crucial details in a shorter, coherent, and natural sounding text. 
Text: I'll begin by discussing our 2020 results, briefly comment on the outlook for 2021, and of course, comment on the pending acquisition of FLIR.
We concluded 2020 with the best earnings, operating margin and cash flow in the company's history.
Compared to last year, fourth quarter earnings increased 13.7%.
Operating margin increased 173 basis points and free cash flow increased 50.7%.
For the full year 2020, GAAP operating margin increased slightly.
Free cash flow increased significantly, 39.1% to $547.5 million.
It is worth emphasizing that full year margin and cash flow performance occurred despite over $33 million in nonrecurring charges, record negative GDP in the second quarter and the constant challenges faced by manufacturers during the COVID-19 pandemic.
We entered 2021 with a clear improvement in demand across the majority of our businesses.
In fact, we received record orders in the fourth quarter and ended 2020 with record backlog.
Q2 orders were $920 million or 1.14 times sales with year-end backlog of $1.7 billion.
While it's still early in 2021, we're expecting continuing recovery in our commercial businesses as well as growth in our government businesses.
In both cases, strongest within our Digital Imaging segment.
Given some caution and conservatism, related to the ongoing tug of war between shutdowns and vaccines, we think a reasonable outlook for the total company's organic growth is between 5% and 6% for 2021.
Of course, the largely pre-COVID comparison in the first quarter will be the most difficult with revenue relatively flat.
Finally, I want to comment on the FLIR acquisition.
We've been watching FLIR since we first entered the Space-based Infrared imaging market in 2006 when we acquired Teledyne Scientific and Imaging.
We believed then and we believe now that our infrared imaging technologies and market segments are uniquely complementary.
As both companies evolved, we've grown to be even more complementary.
For example, Teledyne entered the subsea drone business in 2008 and FLIR entered the airborne unmanned business in 2016, and more recently, the land-based robotics business.
Perhaps more importantly, each company exited unattractive businesses, Teledyne in 2011 and FLIR in 2018.
While our respective sensing technologies and market segments are different, the fundamental desire of our end customers is an image or even better, information.
This is true for extra imaging, infrared imaging, industrial machine vision and even our underwater marine sonar imaging and software businesses.
In other words, there is similarity and synergy in digitization, imaging algorithms, machine learning and other related technologies across each of our organizations.
I will conclude by noting that for 21 years, Teledyne has consistently and predictably compounded earnings and cash flow, and 2020 was no different.
Nevertheless, I have never been more excited about Teledyne's future than I am today with the pending acquisition of FLIR.
Al will now comment on the performance of our four business segments.
In our Instrumentation segment, overall fourth quarter sales decreased 6.2% when compared with last year.
Sales of environmental instruments decreased 6.7% from last year.
However, sales increased 6.9% sequentially from the third quarter.
Compared with last year, sales of certain products, such as wastewater samplers increased.
However, this was more than offset by year-over-year declines and sales of selected industrial products, such as ambient air monitoring instrumentation.
Sales of electronic test and measurement systems increased 3.7% year-over-year to a quarterly record of $70 million.
Sales of marine instrumentation decreased 11.4% in the quarter, due in part to a difficult comparison with the fourth quarter of 2019.
In spite of lower sales, overall Instrumentation segment operating margin increased 262 basis points to a record, 22.3%.
Now turning to the Digital Imaging segment.
Fourth quarter sales decreased 2.3%, and primarily reflect the core sales of X-ray detectors for dental and medical imaging, partially offset by greater sales of infrared and visible detectors for space applications.
GAAP segment operating margin was 21.6%, an increase of 407 basis points year-over-year and also, a record.
Now in the Aerospace and Defense segment, fourth quarter sales declined 14.8% as greater U.S. defense sales were more than offset by a 45% decline in sales of commercial aerospace products as well as lower commercial space sales related to OneWeb.
The GAAP segment operating margin decreased due to lower sales as well as $5.8 million in severance facility consolidation and other contract charges.
In the Engineered Systems segment, fourth quarter revenue increased 26.8%, primarily due to greater sales from defense, nuclear and other manufacturing programs as well as electronic manufacturing services.
Segment operating margin increased 175 basis points compared with last year.
I will first discuss some additional financials for the quarter, not covered by Robert and Al, and then I will discuss our first quarter and full year 2021 outlook.
In the fourth quarter, cash flow from operating activities was $236.4 million compared with cash flow of $167.9 million for the same period of 2019.
Record free cash flow, that is cash from operating activities less capital expenditures, was $217 million in the fourth quarter of 2020 compared with $144 million in 2019.
Capital expenditures were $19.4 million in the fourth quarter compared to $23.9 million for the same period of 2019.
Depreciation and amortization expense was $28.7 million in the fourth quarter compared to $29.3 million for the same period of 2019.
We ended the quarter with $105.4 million of net debt, that is $778.5 million of debt less cash of $673.1 million for a net debt-to-capital ratio of only 3.2%.
Stock option compensation expense was $5.9 million for the fourth quarter of 2020 compared to $5.7 million for the same period of 2019.
Turning to our outlook.
Management currently believes that earnings per share in the first quarter of 2021 will be in the range of $2.55 to $2.60 per share.
And for the full year 2021, our earnings per share outlook is $11.25 to $11.45.
In each case, these do not reflect the pending acquisition of FLIR and related acquisition and financing costs.
The 2021 full year estimated tax rate, excluding discrete items, is expected to be 22.3%.
In addition, we currently expect significantly less discrete tax items in 2021 compared with 2020.
I will now pass the call back to Robert.

user
sees fy earnings per share $11.25 to $11.45.
sees q1 earnings per share $2.55 to $2.60.
issuing full year 2021 diluted earnings per share outlook of $11.25 to $11.45.

assistant