Condensed Parent Company Financial Statements - Statements of Cash Flows (Parent Company Only) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income		$ 199,738	$ 157,870	$ 98,387
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of premises, furniture, and equipment		16,366	15,865	13,995
Net securities losses		0	0
Net securities losses				1,876
Share-based compensation expense	[1]	13,183	12,062	11,223
Tax benefit related to share-based compensation		364	258	349
Net (increase) decrease in other assets		(146,968)	(44,246)	121,577
Net increase (decrease) in other liabilities		108,956	(4,346)	(56,055)
Net cash provided by operating activities		227,109	253,184	234,266
Investing Activities
Purchases of premises, furniture, and equipment		(20,330)	(27,800)	(16,123)
Net cash (paid) received for acquisitions		13,532
Net cash used in investing activities		(1,054,193)	(1,002,386)	(145,780)
Financing Activities
Repurchases of common stock		(33,928)	0	0
Cash dividends paid		(56,540)	(44,293)	(37,129)
Restricted stock activity		(3,830)	(4,421)	(3,659)
Net cash used in financing activities		837,047	691,890	(4,064)
Supplemental Disclosures of Cash Flow Information:
Common stock issued for acquisitions, net of issuance costs		101,496	83,303	534,090
Parent Company
Operating Activities
Net income		199,738	157,870	98,387
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed loss (income) of subsidiaries		7,926	(102,321)	(51,138)
Depreciation of premises, furniture, and equipment		51	42	9
Net securities losses		0	0
Net securities losses				1,523
Share-based compensation expense		13,183	12,062	11,223
Tax benefit related to share-based compensation		364	258	349
Net (increase) decrease in other assets		(67,330)	35,981	18,667
Net increase (decrease) in other liabilities		49,813	(17,942)	(52,377)
Net cash provided by operating activities		203,745	85,950	26,643
Investing Activities
Proceeds from sales and maturities of securities available-for-sale		0	0	42,516
Purchases of premises, furniture, and equipment		0	(61)	(119)
Net cash (paid) received for acquisitions		(19,966)	39	(47,364)
Net cash used in investing activities		(19,966)	(22)	(4,967)
Financing Activities
Repurchases of common stock		(33,928)
Cash dividends paid		(56,540)	(44,293)	(37,129)
Restricted stock activity		(3,830)	(4,421)	(3,952)
Net cash used in financing activities		(94,298)	(48,714)	(41,081)
Cash and Cash Equivalents, Period Increase (Decrease), Total		89,481	37,214	(19,405)
Cash and Cash Equivalents, at Carrying Value, Beginning Balance		158,026	120,812	140,217
Cash and Cash Equivalents, at Carrying Value, Ending Balance		247,507	158,026	120,812
Supplemental Disclosures of Cash Flow Information:
Common stock issued for acquisitions, net of issuance costs		$ 101,496	$ 83,303	$ 534,090

[1] Comprised of restricted stock, restricted stock unit, and performance share awards expense.