Securities (Details 5) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012
Held to maturity securities unrealized losses
Held to maturity securities, Losses less than 12 months, Fair Value
Held to maturity securities, Losses Less than 12 months, Gross Unrealized Losses
Held to maturity securities, Losses 12 months or longer, Fair value	152,768
Held to maturity securities, Losses 12 months or longer, Gross Unrealized Losses	1,096
Held to maturity securities, Total, Fair value	152,768
Held to maturity securities, Total, Gross Unrealized Losses	1,096
Mortgage-backed securities [Member]
Held to maturity securities unrealized losses
Held to maturity securities, Losses less than 12 months, Fair Value
Held to maturity securities, Losses Less than 12 months, Gross Unrealized Losses
Held to maturity securities, Losses 12 months or longer, Fair value	152,768
Held to maturity securities, Losses 12 months or longer, Gross Unrealized Losses	1,096
Held to maturity securities, Total, Fair value	152,768
Held to maturity securities, Total, Gross Unrealized Losses	$ 1,096