Securities (Available for sale securities losses) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 266,964	$ 334,291
Less than 12 months, Unrealized Losses	(7,297)	(7,412)
12 months or longer, Fair Value	134,171	326,585
12 months or longer, Unrealized Losses	(1,927)	(4,899)
Total, Fair Value	401,135	660,876
Total, Unrealized Losses	(9,224)	(12,311)
U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	15,042	6,042
Less than 12 months, Unrealized Losses	(17)	(15)
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Total, Fair Value	15,042	6,042
Total, Unrealized Losses	(17)	(15)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	244,994	327,363
Less than 12 months, Unrealized Losses	(7,208)	(7,391)
12 months or longer, Fair Value	124,196	306,078
12 months or longer, Unrealized Losses	(1,846)	(4,577)
Total, Fair Value	369,190	633,441
Total, Unrealized Losses	(9,054)	(11,968)
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	6,928	886
Less than 12 months, Unrealized Losses	(72)	(6)
12 months or longer, Fair Value	9,975	20,507
12 months or longer, Unrealized Losses	(81)	(322)
Total, Fair Value	16,903	21,393
Total, Unrealized Losses	$ (153)	$ (328)