Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	$ 918,813	$ 437,414
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	9,247	2,350
12 Months or More Fair Value	298,316	561,668
12 Months or More Unrealized Losses	(9,021)	(11,989)
Total Fair Value	1,217,129	999,082
Total Unrealized Losses	(18,268)	(14,339)
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	664,509	258,825
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	7,610	1,287
12 Months or More Fair Value	214,325	279,015
12 Months or More Unrealized Losses	(7,381)	(6,924)
Total Fair Value	878,834	537,840
Total Unrealized Losses	(14,991)	(8,211)
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	48,261	71,026
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	358	543
12 Months or More Fair Value	31,383	44,148
12 Months or More Unrealized Losses	(580)	(982)
Total Fair Value	79,644	115,174
Total Unrealized Losses	(938)	(1,525)
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	193,400	105,250
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	1,128	518
12 Months or More Fair Value	40,034	216,221
12 Months or More Unrealized Losses	(718)	(3,551)
Total Fair Value	233,434	321,471
Total Unrealized Losses	(1,846)	(4,069)
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	10,343	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	136	0
12 Months or More Fair Value	9,794	19,450
12 Months or More Unrealized Losses	(166)	(411)
Total Fair Value	20,137	19,450
Total Unrealized Losses	(302)	(411)
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	2,300	2,313
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	15	2
12 Months or More Fair Value	2,780	2,834
12 Months or More Unrealized Losses	(176)	(121)
Total Fair Value	5,080	5,147
Total Unrealized Losses	$ (191)	$ (123)