Parent Company Financial Statements (Balance Sheet) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets:
Other assets	$ 100,934	$ 77,175
Total assets	5,292,659	5,010,766	$ 4,529,850
Liabilities:
Junior subordinated debentures	22,681	22,681
Contingent consideration liability	0	0	1,404
Other liabilities	97,279	65,131
Total liabilities	4,789,167	4,562,582
Shareholders’ Equity:
Common stock of $.0625 par value; authorized 60,000,000 shares; issued and outstanding 17,363,455 shares in 2019 and 17,302,037 in 2018	1,085	1,081
Paid-in capital	123,281	119,888
Retained earnings	390,363	355,524
Accumulated other comprehensive loss	(11,237)	(28,309)
Total shareholders’ equity	503,492	448,184	$ 413,284	$ 390,804
Total liabilities and shareholders’ equity	$ 5,292,659	$ 5,010,766
Common stock, par value (in dollars per share)	$ 0.0625	$ 0.0625
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	17,363,455	17,302,037
Common stock, shares outstanding (in shares)	17,363,455	17,302,037
Parent Company [Member]
Assets:
Cash on deposit with bank subsidiary	$ 1,838	$ 1,912
Dividends receivable from bank subsidiary	9,575	7,762
Other assets	232	190
Total assets	535,496	479,390
Liabilities:
Junior subordinated debentures	22,681	22,681
Dividends payable	9,252	8,439
Other liabilities	71	86
Total liabilities	32,004	31,206
Shareholders’ Equity:
Common stock of $.0625 par value; authorized 60,000,000 shares; issued and outstanding 17,363,455 shares in 2019 and 17,302,037 in 2018	1,085	1,081
Paid-in capital	123,281	119,888
Retained earnings	390,363	355,524
Accumulated other comprehensive loss	(11,237)	(28,309)
Total shareholders’ equity	503,492	448,184
Total liabilities and shareholders’ equity	535,496	479,390
Bank [Member]
Assets:
Investment in subsidiaries at equity value:	521,969	467,657
Non-bank [Member]
Assets:
Investment in subsidiaries at equity value:	$ 1,882	$ 1,869