Business Segments (Statement of Operations and Total Assets by Reportable Segment) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 99,505	$ 91,785	$ 90,696
Provision for loan losses	1,850	2,400	2,700
Net interest income after provision for loan losses	97,655	89,385	87,996
Noninterest Income	59,015	62,080	65,214
Depreciation and amortization expense	3,777	3,963	3,941
Other noninterest expenses	93,070	94,822	98,397
Total noninterest expense	96,847	98,785	102,338
Income before income taxes	59,823	52,680	50,872
Income tax expense (benefit)	18,999	16,527	15,798
Net income	40,824	36,153	35,074
Total assets at period end	3,586,874	3,188,867	3,071,884
Expenditures for long-lived assets	5,226	1,491	5,110
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	80,500	79,633	79,505
Provision for loan losses	1,850	2,400	2,700
Net interest income after provision for loan losses	78,650	77,233	76,805
Noninterest Income	17,575	30,769	31,727
Depreciation and amortization expense	2,447	2,473	2,384
Other noninterest expenses	52,639	61,976	62,963
Total noninterest expense	55,086	64,449	65,347
Income before income taxes	41,139	43,553	43,185
Income tax expense (benefit)	13,497	14,598	14,670
Net income	27,642	28,955	28,515
Total assets at period end	2,986,453	2,517,059	2,436,280
Expenditures for long-lived assets	3,474	1,286	4,082
Wealth Management Service [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	(24)	7	17
Provision for loan losses	0	0	0
Net interest income after provision for loan losses	(24)	7	17
Noninterest Income	33,378	31,825	29,640
Depreciation and amortization expense	1,127	1,277	1,272
Other noninterest expenses	22,386	20,494	19,584
Total noninterest expense	23,513	21,771	20,856
Income before income taxes	9,841	10,061	8,801
Income tax expense (benefit)	3,724	3,724	3,296
Net income	6,117	6,337	5,505
Total assets at period end	52,720	50,297	51,730
Expenditures for long-lived assets	1,578	112	877
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	19,029	12,145	11,174
Provision for loan losses	0	0	0
Net interest income after provision for loan losses	19,029	12,145	11,174
Noninterest Income	8,062	(514)	3,847
Depreciation and amortization expense	203	213	285
Other noninterest expenses	18,045	12,352	15,850
Total noninterest expense	18,248	12,565	16,135
Income before income taxes	8,843	(934)	(1,114)
Income tax expense (benefit)	1,778	(1,795)	(2,168)
Net income	7,065	861	1,054
Total assets at period end	547,701	621,511	583,874
Expenditures for long-lived assets	$ 174	$ 93	$ 151