Investment Securities Carrying Value (Amortized Cost) and Fair Value by remaining period of contractual maturity (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
AFS Amortized Cost Less than one year	$ 5,799
AFS Amortized Cost One through five years	6,895
AFS Amortized Cost Five through ten years	29,313
AFS Amortized Cost After ten years	67,121
AFS Amortized Cost Total	109,128
AFS Fair Value Less than one year	5,802
AFS Fair Value One through five years	7,058
AFS Fair Value Five through ten years	29,456
AFS Fair Value After ten years	67,620
AFS Fair Value	109,936	85,106
AFS Weighted Average Rate Less than one year	0.35%
AFS Weighted Average Rate One through five years	1.90%
AFS Weighted Average Rate Five through ten years	1.54%
Available-for-sale Securities, Debt Maturities, after Ten Years, Weighted Average Rate	1.36%
AFS Weighted Average Rate Total	1.39%
HTM Amortized Cost Five through ten years	191
HTM Amortized Cost After ten years	9,374
HTM Amortized Cost Total	9,565
HTM Fair Value Five through ten years	199
HTM Fair Value After ten years	9,992
HTM Fair Value Total	$ 10,191
HTM Weighted Average Rate Five through ten years	3.91%
HTM Weighted Average Rate After ten years	4.00%
HTM Weighted Average Rate Total	4.00%