Parent Company Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Income (Loss) Attributable to Parent	$ 23,936	$ 31,146	$ 22,163	$ 25,455	$ 26,261	$ 24,762	$ 28,241	$ 31,123	$ 102,700	$ 110,387	$ 84,242
Share-based Payment Arrangement, Noncash Expense									6,324	5,063	3,942
Debt and Equity Securities, Unrealized Gain (Loss)									(4,204)	(3,267)	0
Increase (Decrease) in Other Operating Assets									(12,305)	(9,413)	1,155
Increase (Decrease) in Other Operating Liabilities									(3,781)	5,131	(11,778)
Net cash provided by operating activities									111,014	131,797	86,686
Payments to Acquire Businesses, Gross									28,630	30,684	0
Other investing activities, net									5,723	60	0
Net cash used in investing activities									60,079	45,445	(60,666)
Repayments of Subordinated Debt									0	0	30,000
Proceeds from Issuance of Long-term Debt									50,000	50,000	150,000
Repayments of Long-term Debt									257,500	150,000	350,000
Payments Related to Tax Withholding for Share-based Compensation									827	610	347
Net cash (used in) provided by financing activities									(178,351)	(179,140)	(3,354)
Increase (decrease) in cash and cash equivalents									(7,258)	(1,898)	22,666
Treasury Stock, Common [Member]
Payments for Repurchase of Equity									40,535	5,784	7,378
Parent Company
Net Income (Loss) Attributable to Parent									102,700	110,387	84,242
Undistributed Losses Of Subsidiaries									16,828	14,270	26,699
Compensation expense for issuance of treasury shares to directors									1,325	1,109	1,241
Share-based Payment Arrangement, Noncash Expense									4,999	3,954	2,701
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments									0	0	(1,821)
Increase (Decrease) in Other Operating Assets									8,544	2,073	(205)
Increase (Decrease) in Other Operating Liabilities									10,006	(163)	475
Net cash provided by operating activities									89,454	95,677	60,344
Proceeds from Sale of Available-for-sale Securities, Equity									0	0	2,265
Net cash used in investing activities									(22,907)	(30,624)	2,265
Payments of Dividends									69,113	63,013	57,493
Proceeds from Issuance of Long-term Debt									50,000
Repayments of Long-term Debt									(7,500)
Cash Payment For Fractional Shares									3	4	6
Payments Related to Tax Withholding for Share-based Compensation									(827)	(610)	(347)
Net cash (used in) provided by financing activities									(67,978)	(69,411)	(95,224)
Increase (decrease) in cash and cash equivalents									(1,431)	(4,358)	(32,615)
Cash	$ 73,663				$ 75,094				$ 73,663	$ 75,094	$ 79,452	$ 112,067