Securities (Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,644,805	$ 1,680,491
Available-for-sale Securities, Gross Unrealized Gain, instant	23,314	22,551
Gross Unrealized Losses	28,749	38,931
Fair Value	1,639,370	1,664,111
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	919,299	961,442
Available-for-sale Securities, Gross Unrealized Gain, instant	10,339	10,640
Gross Unrealized Losses	17,340	23,674
Fair Value	912,298	948,408
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	363,983	357,013
Available-for-sale Securities, Gross Unrealized Gain, instant	12,472	11,450
Gross Unrealized Losses	2,775	3,993
Fair Value	373,680	364,470
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	335,151	335,671
Available-for-sale Securities, Gross Unrealized Gain, instant	477	434
Gross Unrealized Losses	7,642	10,066
Fair Value	327,986	326,039
US Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,088	21,081
Available-for-sale Securities, Gross Unrealized Gain, instant	1	0
Gross Unrealized Losses	786	967
Fair Value	20,303	20,114
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,284	5,284
Available-for-sale Securities, Gross Unrealized Gain, instant	25	27
Gross Unrealized Losses	206	231
Fair Value	$ 5,103	$ 5,080