Securities (Available for sale securities losses) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value
Less than 12 months	$ 645,999	$ 821,737
12 months or longer	180,659	147,022
Total	826,658	968,759
Unrealized Losses
Less than 12 months	(15,303)	(16,566)
12 months or longer	(6,451)	(5,552)
Total	(21,754)	(22,118)
Total debt securities
Fair Value
Less than 12 months	645,999	815,171
12 months or longer	180,659	147,022
Total	826,658	962,193
Unrealized Losses
Less than 12 months	(15,303)	(16,522)
12 months or longer	(6,451)	(5,552)
Total	(21,754)	(22,074)
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	575,105	724,330
12 months or longer	180,406	139,562
Total	755,511	863,892
Unrealized Losses
Less than 12 months	(14,317)	(15,523)
12 months or longer	(6,450)	(5,361)
Total	(20,767)	(20,884)
Obligations of states and political subdivisions
Fair Value
Less than 12 months	70,894	68,482
12 months or longer	253	7,460
Total	71,147	75,942
Unrealized Losses
Less than 12 months	(986)	(896)
12 months or longer	(1)	(191)
Total	(987)	(1,087)
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)