Parent Company Financial Statements (Balance Sheet) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets:
Other assets	$ 77,175	$ 63,740
Total assets	5,010,766	4,529,850	$ 4,381,115
Liabilities:
Junior subordinated debentures	22,681	22,681
Contingent consideration liability	0	1,404	2,047
Other liabilities	65,131	59,822
Total liabilities	4,562,582	4,116,566
Shareholders’ Equity:
Common stock of $.0625 par value; authorized 60,000,000 shares; issued and outstanding 17,302,037 shares in 2018 and 17,226,508 shares in 2017	1,081	1,077
Paid-in capital	119,888	117,961
Retained earnings	355,524	317,756
Accumulated other comprehensive loss	(28,309)	(23,510)
Total shareholders’ equity	448,184	413,284	$ 390,804	$ 375,388
Total liabilities and shareholders’ equity	$ 5,010,766	$ 4,529,850
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)	17,302,037	17,226,508
Common stock, shares outstanding (in shares)	17,302,037	17,226,508
Parent Company [Member]
Assets:
Cash on deposit with bank subsidiary	$ 1,912	$ 1,664
Dividends receivable from bank subsidiary	7,762	7,770
Other assets	190	259
Total assets	479,390	444,524
Liabilities:
Junior subordinated debentures	22,681	22,681
Dividends payable	8,439	7,087
Contingent consideration liability	0	1,404
Other liabilities	86	68
Total liabilities	31,206	31,240
Shareholders’ Equity:
Common stock of $.0625 par value; authorized 60,000,000 shares; issued and outstanding 17,302,037 shares in 2018 and 17,226,508 shares in 2017	1,081	1,077
Paid-in capital	119,888	117,961
Retained earnings	355,524	317,756
Accumulated other comprehensive loss	(28,309)	(23,510)
Total shareholders’ equity	448,184	413,284
Total liabilities and shareholders’ equity	479,390	444,524
Bank [Member]
Assets:
Investment in subsidiaries at equity value:	467,657	433,010
Non-bank [Member]
Assets:
Investment in subsidiaries at equity value:	$ 1,869	$ 1,821