Investment Securities Carrying Value (Amortized Cost) and Fair Value by remaining period of contractual maturity (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
AFS Amortized Cost Less than one year	$ 3,103
AFS Amortized Cost One through five years	9,898
AFS Amortized Cost Five through ten years	30,615
AFS Amortized Cost After ten years	70,174
AFS Amortized Cost Total	113,790
AFS Fair Value Less than one year	3,105
AFS Fair Value One through five years	10,074
AFS Fair Value Five through ten years	30,778
AFS Fair Value After ten years	70,505
AFS Fair Value	114,462	85,106
AFS Weighted Average Rate Less than one year	0.39%
AFS Weighted Average Rate One through five years	1.53%
AFS Weighted Average Rate Five through ten years	1.58%
Available-for-sale Securities, Debt Maturities, after Ten Years, Weighted Average Rate	1.46%
AFS Weighted Average Rate Total	1.46%
HTM Amortized Cost Five through ten years	204
HTM Amortized Cost After ten years	9,834
HTM Amortized Cost Total	10,038
HTM Fair Value Five through ten years	214
HTM Fair Value After ten years	10,523
HTM Fair Value Total	$ 10,737
HTM Weighted Average Rate Five through ten years	3.92%
HTM Weighted Average Rate After ten years	4.09%
HTM Weighted Average Rate Total	4.09%