Investment Securities Carrying Value (Amortized Cost) and Fair Value by remaining period of contractual maturity (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
AFS Amortized Cost Less than one year	$ 3,104
AFS Amortized Cost One through five years	14,891
AFS Amortized Cost Five through ten years	14,896
AFS Amortized Cost After ten years	57,661
AFS Amortized Cost Total	90,552
AFS Fair Value Less than one year	3,108
AFS Fair Value One through five years	15,002
AFS Fair Value Five through ten years	14,983
AFS Fair Value After ten years	57,740
AFS Fair Value	90,833	85,106
AFS Weighted Average Rate Less than one year	0.39%
AFS Weighted Average Rate One through five years	1.37%
AFS Weighted Average Rate Five through ten years	1.50%
Available-for-sale Securities, Debt Maturities, after Ten Years, Weighted Average Rate	1.54%
AFS Weighted Average Rate Total	1.46%
HTM Amortized Cost Five through ten years	217
HTM Amortized Cost After ten years	10,184
HTM Amortized Cost Total	10,401
HTM Fair Value Five through ten years	227
HTM Fair Value After ten years	10,864
HTM Fair Value Total	$ 11,091
HTM Weighted Average Rate Five through ten years	4.02%
HTM Weighted Average Rate After ten years	4.09%
HTM Weighted Average Rate Total	4.09%