Goodwill and Other Intangible Assets - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Gross carrying value, core deposit intangibles	$ 11,508	$ 11,508
Accumulated amortization, core deposit intangibles	(10,317)	(9,789)
Net carrying value, core deposit intangibles	1,191	1,719
Gross carrying value, goodwill	43,872	43,872
Accumulated amortization, goodwill	0	0
Net carrying value, goodwill	$ 43,872	$ 43,872	$ 43,872