Goodwill and Other Intangible Assets - Amortized Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Amortized intangible assets:
Balance at the beginning of period	$ 32,873
Amortization of intangible assets	9,547	$ 5,854	$ 5,245
Balance at the end of period	61,593	32,873
Core deposit intangible assets
Amortized intangible assets:
Balance at the beginning of period	31,836
Amortization of intangible assets	7,963	5,535
Balance at the end of period	51,100	31,836
Customer relationship intangible assets
Amortized intangible assets:
Balance at the beginning of period	1,037
Amortization of intangible assets	1,584	319
Balance at the end of period	$ 10,493	$ 1,037