Other Borrowings - Schedule of Company's Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Overnight FHLB advances	$ 587,742	$ 503,815
Term FHLB advances	475,000	365,000
Other	9,000	16,000
Total other borrowings	$ 1,071,742	$ 884,815