Goodwill and Other Intangible Assets - Summary of Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	$ 84,962	$ 84,962
Accumulated Amortization	(53,164)	(47,702)
Net Carrying Amount	31,798	37,260
Core deposit intangibles
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	82,492	82,492
Accumulated Amortization	(51,925)	(46,599)
Net Carrying Amount	30,567	35,893
Customer relationship intangible
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	2,470	2,470
Accumulated Amortization	(1,239)	(1,103)
Net Carrying Amount	$ 1,231	$ 1,367