Noninterest Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Noninterest Income [Abstract]
Service charges and fees on deposit accounts									$ 19,581	$ 18,452	$ 18,562
Wealth management revenue									11,763	11,104	10,106
Electronic banking fees									6,981	6,637	5,765
Mortgage banking revenue									6,597	3,881	3,925
Other fees for customer services									2,598	2,451	2,461
Insurance commissions									1,836	1,413	1,373
Gain on sale of merchant card services									1,280	0	0
Other									1,236	462	280
Total Noninterest Income	$ 13,879	$ 12,062	$ 13,282	$ 12,649	$ 11,501	$ 11,225	$ 10,902	$ 10,772	$ 51,872	$ 44,400	$ 42,472