Securities Fair Value Option Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	$ 210,192	$ 284,296	$ 347,952
Fair Value Option Securities, Unrealized Gain or Loss	772	4,770	2,271
U.S. Agency Residential Mortgage-backed Securities [Member]
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	208,900	257,040	322,180
Fair Value Option Securities, Unrealized Gain or Loss	726	3,314	1,593
Corporate Debt Securities [Member]
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	0	26,486	25,772
Fair Value Option Securities, Unrealized Gain or Loss	0	1,409	678
Other Debt Securities [Member]
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	1,292	770	0
Fair Value Option Securities, Unrealized Gain or Loss	$ 46	$ 47	$ 0