Securities (Available for sale securities losses) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value
Less than 12 months	$ 528,410	$ 821,737
12 months or longer	137,259	147,022
Total	665,669	968,759
Unrealized Losses
Less than 12 months	(8,406)	(16,566)
12 months or longer	(4,215)	(5,552)
Total	(12,621)	(22,118)
U.S. government corporations and agencies
Fair Value
Less than 12 months	0	22,359
12 months or longer	0	0
Total	0	22,359
Unrealized Losses
Less than 12 months	0	(103)
12 months or longer	0	0
Total	0	(103)
Mortgage-backed securities
Fair Value
Less than 12 months	517,907	724,330
12 months or longer	130,640	139,562
Total	648,547	863,892
Unrealized Losses
Less than 12 months	(8,323)	(15,523)
12 months or longer	(4,145)	(5,361)
Total	(12,468)	(20,884)
Obligations of states and political subdivisions
Fair Value
Less than 12 months	10,003	68,482
12 months or longer	6,619	7,460
Total	16,622	75,942
Unrealized Losses
Less than 12 months	(82)	(896)
12 months or longer	(70)	(191)
Total	(152)	(1,087)
Corporate debt securities
Fair Value
Less than 12 months	500	0
12 months or longer	0	0
Total	500	0
Unrealized Losses
Less than 12 months	(1)	0
12 months or longer	0	0
Total	(1)	0
Total debt securities
Fair Value
Less than 12 months	528,410	815,171
12 months or longer	137,259	147,022
Total	665,669	962,193
Unrealized Losses
Less than 12 months	(8,406)	(16,522)
12 months or longer	(4,215)	(5,552)
Total	(12,621)	(22,074)
Equity securities
Fair Value
Less than 12 months	0	6,566
12 months or longer	0	0
Total	0	6,566
Unrealized Losses
Less than 12 months	0	(44)
12 months or longer	0	0
Total	$ 0	$ (44)