SQLServer - Multiple PIVOT on same column
Group by Header and Subheader and take the sum like below
SELECT Header, SubHeader,
  Sum(Regular), Sum(Irregular),
  Sum(FRegular), Sum(FIrregular),
  Sum(MrRegular), Sum(MrIrregular)
  FROM (SELECT Header, 
               SubHeader, 
               Type, 'F'+Type AS FType, 
               'Mr'+Type as MType, 
               'Ap'+Type AType, 
               'Ma'+Type as May,
               January], [February], [March] 
  from [CashFlow].[dbo].[Details] ) p

  PIVOT (MAX(January) FOR Type in (Regular, Irregular)) AS JPVT
  PIVOT (MAX([February]) FOR FType in (FRegular, FIrregular)) AS FPVT
  PIVOT (MAX(March) FOR MType in (MrRegular, MrIrregular)) AS MrPVT
Group by Header, SubHeader