Securities (Available for sale securities losses) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 725,959	$ 1,034,016
Less than 12 months, Unrealized Losses	(11,596)	(30,517)
12 months or longer, Fair Value	158,816	128,943
12 months or longer, Unrealized Losses	(6,073)	(6,460)
Total, Fair Value	884,775	1,162,959
Total, Unrealized Losses	(17,669)	(36,977)
U.S. Government Corporations and Agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	130,411	196,345
Less than 12 months, Unrealized Losses	(769)	(2,001)
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Total, Fair Value	130,411	196,345
Total, Unrealized Losses	(769)	(2,001)
Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	506,526	640,684
Less than 12 months, Unrealized Losses	(8,413)	(17,064)
12 months or longer, Fair Value	132,248	118,229
12 months or longer, Unrealized Losses	(4,696)	(5,510)
Total, Fair Value	638,774	758,913
Total, Unrealized Losses	(13,109)	(22,574)
Obligations of States and Political Subdivisions
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	89,022	196,987
Less than 12 months, Unrealized Losses	(2,414)	(11,452)
12 months or longer, Fair Value	26,568	10,714
12 months or longer, Unrealized Losses	(1,377)	(950)
Total, Fair Value	115,590	207,701
Total, Unrealized Losses	$ (3,791)	$ (12,402)