Deposits - Total deposits - (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Deposits Disclosure Abstract
Certificates of deposit	$ 1,060,048	$ 872,773	$ 1,033,109
Interest-bearing demand deposits	3,981,920	3,461,004	3,338,433
Non-interest bearing demand deposits	2,599,111	2,199,046	2,020,632
Savings deposits	1,388,388	799,615	766,752
Other time deposits	3,971	1,985	3,022
Total deposits	$ 9,033,438	$ 7,334,423	$ 7,161,948