Deposits - Schedule of Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Banking and Thrift [Abstract]
Demand deposits	$ 3,746,654	$ 2,866,853
Savings deposits	1,994,366	1,560,752
Certificates and other time deposits of $100,000 or more	468,895	276,274
Other certificates and time deposits	581,894	471,247
Brokered deposits	380,721	381,372
Total Deposits	7,172,530	5,556,498
Cash amount that exceeded federally insured limits	$ 3,200,000	$ 2,200,000