Business Combinations - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Feb. 01, 2020	May 01, 2019	Apr. 02, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Nov. 01, 2018	Oct. 02, 2018	May 01, 2018
Business Acquisition [Line Items]
Goodwill				$ 349,398	$ 236,347	$ 150,601
Loans				28,881,496	25,523,276
Deposits				34,431,236	30,672,460
Merger-related expenses				17,166	6,462	$ 9,015
Community Financial Holding Co. Inc. | Subsequent Event
Business Acquisition [Line Items]
Cash paid to acquire business	$ 2,300
Total assets acquired	224,000
Loans	136,900
Deposits acquired	$ 211,800
Entegra Financial
Business Acquisition [Line Items]
Total assets acquired				1,681,324
Deposits acquired				$ 1,326,967
Share price (usd per share)				$ 30.18
Purchase Price				$ 222,750
Non-PCI loans acquired				953,700
PCI loans acquired				77,500
Intangible assets				4,500
Total liabilities assumed				1,511,208
Goodwill				52,634
Loans				1,031,186
Merger-related expenses				5,400
Intangible assets				6,899
First South Bancorp
Business Acquisition [Line Items]
Total assets acquired		$ 239,151
Deposits acquired		$ 207,556
Share price (usd per share)		$ 1.15
Purchase Price		$ 37,486
Non-PCI loans acquired		162,800
PCI loans acquired		16,400
Intangible assets		2,268
Total liabilities assumed		215,561		1,067	0
Goodwill		13,896
Loans		$ 179,243
Interest And Fee Income, Loans, Consumer And Commercial				6,100
Merger-related expenses				4,100
Biscayne Bancshares
Business Acquisition [Line Items]
Total assets acquired			$ 1,029,184
Share price (usd per share)			$ 25.05
Purchase Price			$ 118,949
Non-PCI loans acquired			850,400
PCI loans acquired			13,000
Intangible assets			4,700
Total liabilities assumed			956,756	1,138	0
Goodwill			46,521
Loans			863,384
Deposits			786,500
Interest And Fee Income, Loans, Consumer And Commercial				33,800
Deposits			786,512
Merger-related expenses				5,800
Intangible assets			$ 4,745
Palmetto Heritage Bancshares
Business Acquisition [Line Items]
Total assets acquired							$ 162,200
Deposits acquired							124,900
Non-PCI loans acquired							131,300
PCI loans acquired							3,900
Total liabilities assumed							149,300
Goodwill							17,500
Merger-related expenses				600	500
Revenue of acquired business				5,600	1,200
Palmetto Heritage Bancshares | Core deposits
Business Acquisition [Line Items]
Intangible assets							$ 1,700
Capital Commerce Bancorp
Business Acquisition [Line Items]
Total assets acquired								$ 221,900
Deposits acquired								172,400
Non-PCI loans acquired								173,400
PCI loans acquired								10,800
Total liabilities assumed				0	808			204,500
Goodwill								10,700
Merger-related expenses				700	1,200
Revenue of acquired business				8,100	3,200
Capital Commerce Bancorp | Core deposits
Business Acquisition [Line Items]
Intangible assets								$ 2,700
HomeBancorp Inc.
Business Acquisition [Line Items]
Total assets acquired									$ 842,700
Deposits acquired									619,600
Non-PCI loans acquired									550,600
PCI loans acquired									15,600
Total liabilities assumed									787,700
Goodwill									57,600
Merger-related expenses				100	2,300
Revenue of acquired business				21,400	$ 17,400
HomeBancorp Inc. | Core deposits
Business Acquisition [Line Items]
Intangible assets									$ 9,900
North Carolina Branches
Business Acquisition [Line Items]
Loans and leases				106,400
Premises and equipment				2,300
Deposits				$ 186,400