Goodwill and Intangible Assets - Summary of Carrying Amount of Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 14,747	$ 332
Core deposit intangible
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	14,452	0
Customer lists
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 295	$ 332