Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	$ (23,314)	$ (22,551)
Less than 12 Months Fair Value	760,614	887,693
Less than 12 Months Unrealized Losses	(15,938)	(23,148)
12 Months or More Fair Value	162,043	166,348
12 Months or More Unrealized Losses	(12,811)	(15,783)
Total Fair Value	922,657	1,054,041
Total Unrealized Losses	(28,749)	(38,931)
Available-for-sale Debt Securities, Gross Unrealized Loss, instant	(28,749)	(38,931)
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	(10,339)	(10,640)
Less than 12 Months Fair Value	399,830	492,921
Less than 12 Months Unrealized Losses	(7,290)	(10,991)
12 Months or More Fair Value	112,690	121,303
12 Months or More Unrealized Losses	(10,050)	(12,684)
Total Fair Value	512,520	614,224
Total Unrealized Losses	(17,340)	(23,675)
Available-for-sale Debt Securities, Gross Unrealized Loss, instant	(17,340)	(23,674)
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	(12,472)	(11,450)
Less than 12 Months Fair Value	88,065	112,400
Less than 12 Months Unrealized Losses	(1,791)	(3,069)
12 Months or More Fair Value	17,748	13,815
12 Months or More Unrealized Losses	(984)	(923)
Total Fair Value	105,813	126,215
Total Unrealized Losses	(2,775)	(3,992)
Available-for-sale Debt Securities, Gross Unrealized Loss, instant	(2,775)	(3,993)
US Government Corporations and Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	(477)	(434)
Less than 12 Months Fair Value	251,196	260,001
Less than 12 Months Unrealized Losses	(6,026)	(8,063)
12 Months or More Fair Value	28,810	28,447
12 Months or More Unrealized Losses	(1,616)	(2,003)
Total Fair Value	280,006	288,448
Total Unrealized Losses	(7,642)	(10,066)
Available-for-sale Debt Securities, Gross Unrealized Loss, instant	(7,642)	(10,066)
US Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	(1)	0
Less than 12 Months Fair Value	19,253	20,114
Less than 12 Months Unrealized Losses	(786)	(967)
12 Months or More Fair Value	0	0
12 Months or More Unrealized Losses	0	0
Total Fair Value	19,253	20,114
Total Unrealized Losses	(786)	(967)
Available-for-sale Debt Securities, Gross Unrealized Loss, instant	(786)	(967)
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	(25)	(27)
Less than 12 Months Fair Value	2,270	2,257
Less than 12 Months Unrealized Losses	(45)	(58)
12 Months or More Fair Value	2,795	2,783
12 Months or More Unrealized Losses	(161)	(173)
Total Fair Value	5,065	5,040
Total Unrealized Losses	(206)	(231)
Available-for-sale Debt Securities, Gross Unrealized Loss, instant	$ (206)	$ (231)