Other Intangibles - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Jul. 14, 2017	May 19, 2017
Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life of core deposit intangibles and other intangibles	2 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life of core deposit intangibles and other intangibles	10 years
IAB
Finite-Lived Intangible Assets [Line Items]
Core deposit intangible		$ 17,403
IAB | Core deposit intangibles acquired
Finite-Lived Intangible Assets [Line Items]
Core deposit intangible		13,638
IAB | Other intangibles acquired
Finite-Lived Intangible Assets [Line Items]
Core deposit intangible		$ 3,765
Arlington Bank
Finite-Lived Intangible Assets [Line Items]
Core deposit intangible			$ 4,526
Arlington Bank | Core deposit intangibles acquired
Finite-Lived Intangible Assets [Line Items]
Core deposit intangible			$ 4,526