Goodwill and Other Intangible Assets - Goodwill and Other Intangibles (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Total	$ 127,340	$ 91,334
Core deposit intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	148,679	105,984
Accumulated amortization	(36,871)	(26,177)
Total	111,808	79,807	$ 89,325
Books of Business Intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	20,350	15,234
Accumulated amortization	(4,818)	(3,707)
Total	$ 15,532	$ 11,527	$ 16,746