Investment Securities (Narrative) (Details) (USD $)	12 Months Ended					3 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009		Dec. 31, 2011 29 Non-Agency Residential Collateralized Mortgage Obligations [Member]	Mar. 31, 2009 Three Non-Agency Residential Collateralized Mortgage Obligations [Member]
OTTI recognized on investment securities held to maturity	$ 190,000	$ 93,000	$ 12,317,000		$ 8,200,000	$ 2,100,000
Adverse ratings change	0
OTTI charge related to an available for sale			239,000
OTTI charges recorded on available for sale securities			239,000	[1]
Underlying mortgages of held-to-maturity securities with other-than-temporary impairment, loan-to-value	69.00%
Underlying borrowers, FICO score, weighted average	731
Portion of underlying mortgages with limited documentation	59.00%
Carrying value of investment securities pledged	$ 1,100,000,000	$ 1,500,000,000

[1] Represents other-than-temporary impairment losses related to credit losses.