Parent Company Financial Statements, Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets [Abstract]
Cash on deposit	$ 48,603	$ 51,974
Goodwill	65,490	65,490
Premises and equipment, net	47,940	48,188
Other assets	36,984	33,827
Total assets	3,932,169	3,903,934
Liabilities and shareholders' equity [Abstract]
Long-term debt	61,341	61,341
Other liabilities	24,244	21,431
Total liabilities	3,431,554	3,428,351
Shareholders' equity	500,615	475,583
Total liabilities and shareholders' equity	3,932,169	3,903,934
Parent Company [Member]
Assets [Abstract]
Cash on deposit	1,525	1,462
Investment in and advances to subsidiaries	556,975	531,702
Goodwill	4,973	4,973
Premises and equipment, net	142	145
Other assets	391	911
Total assets	564,006	539,193
Liabilities and shareholders' equity [Abstract]
Long-term debt	61,341	61,341
Other liabilities	2,050	2,269
Total liabilities	63,391	63,610
Shareholders' equity	500,615	475,583
Total liabilities and shareholders' equity	$ 564,006	$ 539,193