Fair Value Measurements - Fair Value, Financial Instruments, Unobservable Input Reconciliation (Details) (Recurring basis, USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Securities available for sale, at fair value
Level 3 Financial Instruments Measured at Fair Value
Beginning balance	$ 6,763,000	$ 7,520,000
Total gains (losses):
Included in other comprehensive income	22,000	(1,126,000)
Purchases, sales, issuances and settlements:
Purchases	0	4,924,000
Transfer in and/or out of Level 3	(3,736,000)	(4,555,000)
Ending Balance	3,049,000	6,763,000
Change in unrealized gains relating to assets still held at the reporting date	22,000	(1,126,000)
State tax credits held for sale
Level 3 Financial Instruments Measured at Fair Value
Beginning balance	26,350,000	31,576,000
Total gains (losses):
Included in earnings	1,192,000	2,292,000
Purchases, sales, issuances and settlements:
Sales	(4,522,000)	(7,518,000)
Ending Balance	23,020,000	26,350,000
Change in unrealized gains relating to assets still held at the reporting date	$ 80,000	$ 436,000