Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	$ 887,693	$ 254,666
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	23,148	5,923
12 Months or More Fair Value	166,348	13,378
12 Months or More Unrealized Losses	(15,783)	(377)
Total Fair Value	1,054,041	268,044
Total Unrealized Losses	(38,931)	(6,300)
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	492,921	167,739
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	10,991	5,090
12 Months or More Fair Value	121,303	12,204
12 Months or More Unrealized Losses	(12,684)	(336)
Total Fair Value	614,224	179,943
Total Unrealized Losses	(23,675)	(5,426)
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	112,400	20,413
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	3,069	383
12 Months or More Fair Value	13,815	210
12 Months or More Unrealized Losses	(923)	(5)
Total Fair Value	126,215	20,623
Total Unrealized Losses	(3,992)	(388)
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	260,001	56,600
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	8,063	435
12 Months or More Fair Value	28,447	0
12 Months or More Unrealized Losses	(2,003)	0
Total Fair Value	288,448	56,600
Total Unrealized Losses	(10,066)	(435)
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	20,114	9,914
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	967	15
12 Months or More Fair Value	0	0
12 Months or More Unrealized Losses	0	0
Total Fair Value	20,114	9,914
Total Unrealized Losses	(967)	(15)
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	2,257	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	58	0
12 Months or More Fair Value	2,783	964
12 Months or More Unrealized Losses	(173)	(36)
Total Fair Value	5,040	964
Total Unrealized Losses	$ (231)	$ (36)