Parent Company Financial Information (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets:
Deferred income tax benefits	$ 3,447
Other assets	16,143	$ 24,925
Total assets	4,241,060	3,894,708
Liabilities:
Cash dividends payable	4,456	3,798	$ 3,368
Total liabilities	3,852,873	3,540,258
Stockholders' Equity:
Common stock	2,542	2,467
Surplus	145,163	127,122
Retained earnings	249,922	224,315
Total	397,627	353,904
Accumulated other comprehensive income (loss), net of tax	(9,440)	546
Total	388,187	354,450	305,830	$ 250,936
Total	4,241,060	3,894,708
Parent Company [Member]
Assets:
Cash and due from banks	583	925
Investment in subsidiary bank, at equity	390,388	354,334
Prepaid income taxes		1,552
Deferred income tax benefits	1,924	1,381
Other assets	80	81
Total assets	392,975	358,273
Liabilities:
Other liabilities	332	25
Cash dividends payable	4,456	3,798	$ 3,368
Total liabilities	4,788	3,823
Stockholders' Equity:
Common stock	2,542	2,467
Surplus	145,163	127,122
Retained earnings	249,922	224,315
Total	397,627	353,904
Accumulated other comprehensive income (loss), net of tax	(9,440)	546
Total	388,187	354,450
Total	$ 392,975	$ 358,273