Condensed Financial Information (parent company only) - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash Flow From Operating Activities:
Net income	$ 205,531	$ 148,600	$ 164,460
Adjustments to reconcile net income to net cash provided by operating activities
Share-based compensation	4,762	4,600	4,115
Net cash provided by operating activities	207,382	203,831	176,727
Cash Flow From Investing Activities:
Net cash used in investing activities	(1,469,446)	(1,552,025)	(1,006,399)
Cash Flows from Financing Activities:
Repayment of borrowings	(96,204)	(621,548)	(643,169)
Stock issued under employee benefit plans	605	639	702
Stock issued under dividend reinvestment and stock purchase plan	1,880	1,726	1,531
Stock options exercised	198	115	144
Repurchase of common stock	(25,444)	(55,912)	(19,041)
Net cash provided by financing activities	1,236,314	1,363,889	867,626
Net Change in Cash and Cash Equivalents	(25,750)	15,695	37,954
Cash and Cash Equivalents, January 1	192,896	177,201	139,247
Cash and Cash Equivalents, December 31	167,146	192,896	177,201
Parent
Cash Flow From Operating Activities:
Net income	205,531	148,600	164,460
Adjustments to reconcile net income to net cash provided by operating activities
Share-based compensation	1,563	1,502	1,339
Distributions in excess of (equity in undistributed) income of subsidiaries	(55,162)	(89,465)	(51,368)
Other adjustments	(1,173)	1,537	(6,013)
Investment in subsidiaries - operating activities	885	235	(268)
Net cash provided by operating activities	151,644	62,409	108,150
Cash Flow From Investing Activities:
Net cash received in acquisition	0	0	78
Net cash used in investing activities	0	0	78
Cash Flows from Financing Activities:
Cash dividends	(61,230)	(56,542)	(51,276)
Repayment of borrowings	0	(20,310)	0
Stock issued under employee benefit plans	605	639	702
Stock issued under dividend reinvestment and stock purchase plan	1,880	1,726	1,531
Stock options exercised	198	115	144
Repurchase of common stock	(25,444)	(55,912)	(19,041)
Net cash provided by financing activities	(83,991)	(130,284)	(67,940)
Net Change in Cash and Cash Equivalents	67,653	(67,875)	40,288
Cash and Cash Equivalents, January 1	59,848	127,723	87,435
Cash and Cash Equivalents, December 31	$ 127,501	$ 59,848	$ 127,723