Goodwill and Other Intangible Assets - Textual (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Oct. 31, 2019	Oct. 30, 2019	Apr. 12, 2019
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 1,064,978	$ 1,055,520
Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	10 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	15 years
Core Deposit Premium | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	10 years
Core Deposit Premium | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	15 years
Landrum Company
Finite-Lived Intangible Assets [Line Items]
Goodwill		131,300	$ 140,797	$ 407
Goodwill increase	$ 9,500
Reliance Bancshares, Inc.
Finite-Lived Intangible Assets [Line Items]
Goodwill		$ 78,500			$ 78,493