Securities (Available for sale securities losses) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 465,913	$ 334,291
Less than 12 months, Unrealized Losses	(8,687)	(7,412)
12 months or longer, Fair Value	138,327	326,585
12 months or longer, Unrealized Losses	(2,450)	(4,899)
Total, Fair Value	604,240	660,876
Total, Unrealized Losses	(11,137)	(12,311)
U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	0	6,042
Less than 12 months, Unrealized Losses	0	(15)
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Total, Fair Value	0	6,042
Total, Unrealized Losses	0	(15)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	390,432	327,363
Less than 12 months, Unrealized Losses	(7,343)	(7,391)
12 months or longer, Fair Value	128,712	306,078
12 months or longer, Unrealized Losses	(2,017)	(4,577)
Total, Fair Value	519,144	633,441
Total, Unrealized Losses	(9,360)	(11,968)
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	75,481	886
Less than 12 months, Unrealized Losses	(1,344)	(6)
12 months or longer, Fair Value	9,615	20,507
12 months or longer, Unrealized Losses	(433)	(322)
Total, Fair Value	85,096	21,393
Total, Unrealized Losses	$ (1,777)	$ (328)