Securities (Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 969,359	$ 987,560
Gross Unrealized Gains	38,606	42,638
Gross Unrealized Losses	(6,300)	(2,088)
Fair Value	1,001,665	1,028,110
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross realized losses	714	250	148
Gross realized gains	4,400	384	206
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	561,076	678,631
Gross Unrealized Gains	16,719	19,323
Gross Unrealized Losses	(5,426)	(2,000)
Fair Value	572,369	695,954
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	265,070	263,075
Gross Unrealized Gains	20,893	22,746
Gross Unrealized Losses	(388)	(58)
Fair Value	285,575	285,763
U.S. Government Agency and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	120,085	42,558
Gross Unrealized Gains	851	505
Gross Unrealized Losses	(435)	0
Fair Value	120,501	43,063
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,804
Gross Unrealized Gains	39
Gross Unrealized Losses	(15)
Fair Value	19,828
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,324	3,296
Gross Unrealized Gains	104	64
Gross Unrealized Losses	(36)	(30)
Fair Value	$ 3,392	$ 3,330