Deposits - Total deposits - (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Deposits Disclosure Abstract
Certificates of deposit	$ 911,453	$ 1,092,750	$ 1,159,285
Interest-bearing demand deposits	3,358,647	3,293,942	3,260,482
Non-interest bearing demand deposits	2,176,155	1,976,480	1,927,309
Savings deposits	795,754	735,961	726,373
Other time deposits	5,397	1,295	4,560
Total deposits	$ 7,247,406	$ 7,100,428	$ 7,078,009