Business Segments (Statement of Operations and Total Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 31,852	$ 28,679
Provision for loan losses	0	400
Net interest income after provision for loan losses	31,852	28,279
Noninterest income	15,743	14,510
Depreciation and amortization expense	1,075	1,178
Other noninterest expenses related to segments	26,055	24,108
Total noninterest expense	27,130	25,286
Income before income taxes	20,465	17,503
Income tax expense	4,254	5,721
Net income	16,211	11,782
Total assets	4,566,326	4,388,763	$ 4,529,850
Expenditures for long-lived assets	811	733
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	25,976	23,557
Provision for loan losses	0	400
Net interest income after provision for loan losses	25,976	23,157
Noninterest income	4,936	4,442
Depreciation and amortization expense	637	663
Other noninterest expenses related to segments	15,466	14,607
Total noninterest expense	16,103	15,270
Income before income taxes	14,809	12,329
Income tax expense	3,103	4,029
Net income	11,706	8,300
Total assets	3,521,309	3,344,773
Expenditures for long-lived assets	598	373
Wealth Management Services [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	(58)	(32)
Provision for loan losses	0	0
Net interest income after provision for loan losses	(58)	(32)
Noninterest income	10,273	9,477
Depreciation and amortization expense	396	463
Other noninterest expenses related to segments	7,199	6,448
Total noninterest expense	7,595	6,911
Income before income taxes	2,620	2,534
Income tax expense	643	978
Net income	1,977	1,556
Total assets	66,567	64,984
Expenditures for long-lived assets	154	302
Corporate [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	5,934	5,154
Provision for loan losses	0	0
Net interest income after provision for loan losses	5,934	5,154
Noninterest income	534	591
Depreciation and amortization expense	42	52
Other noninterest expenses related to segments	3,390	3,053
Total noninterest expense	3,432	3,105
Income before income taxes	3,036	2,640
Income tax expense	508	714
Net income	2,528	1,926
Total assets	978,450	979,006
Expenditures for long-lived assets	$ 59	$ 58