Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2019	Oct. 30, 2019	Apr. 12, 2019
Goodwill [Line Items]
Goodwill	$ 1,055,520	$ 845,687
Amortization of intangibles	$ 11,805	11,009	$ 7,668
Minimum
Goodwill [Line Items]
Finite-lived intangible asset, useful life	10 years
Maximum
Goodwill [Line Items]
Finite-lived intangible asset, useful life	15 years
Core deposit intangible
Goodwill [Line Items]
Amortization of intangibles	$ 10,694	9,518	6,000
Core deposit intangible | Minimum
Goodwill [Line Items]
Finite-lived intangible asset, useful life	10 years
Core deposit intangible | Maximum
Goodwill [Line Items]
Finite-lived intangible asset, useful life	15 years
Books of Business Intangible
Goodwill [Line Items]
Amortization of intangibles	$ 1,111	$ 1,370	$ 1,600
Landrum Company
Goodwill [Line Items]
Goodwill	131,300			$ 131,340	$ 407
Reliance Bancshares, Inc.
Goodwill [Line Items]
Goodwill	$ 78,500					$ 78,493