Loans and Allowances for Credit Losses, Troubled Debt Restructurings (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	$ 122,609	$ 109,754	$ 114,350
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	53,578	45,941	41,719
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	69,031	63,813	72,631
Troubled Debt Restructuring, Specific allowance	259	3,404	285
Troubled Debt Restructuring, Charge-offs	33	289
Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	42,384	54,247	40,365
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	29,095	30,292	24,445
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	13,289	23,955	15,920
Troubled Debt Restructuring, Specific allowance	259	3,404	285
Troubled Debt Restructuring, Charge-offs	33	289
Commercial [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	5,802	6,152	6,061
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	4,230	1,412	4,423
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	1,572	4,740	1,638
Troubled Debt Restructuring, Specific allowance	157	3,157	157
Troubled Debt Restructuring, Charge-offs	0	0
Energy [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	0	0	0
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	0	0	0
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	0	0	0
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	0
Services [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	1,617	1,811	1,666
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	687	761	706
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	930	1,050	960
Troubled Debt Restructuring, Specific allowance	148	148	148
Troubled Debt Restructuring, Charge-offs	0	0
Wholesale/retail [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	3,224	207	3,381
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	3,131	73	3,284
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	93	134	97
Troubled Debt Restructuring, Specific allowance	9	9	9
Troubled Debt Restructuring, Charge-offs	0	0
Manufacturing [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	325	3,384	340
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	325	384	340
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	0	3,000	0
Troubled Debt Restructuring, Specific allowance	0	3,000	0
Troubled Debt Restructuring, Charge-offs	0	0
Healthcare [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	0	0	0
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	0	0	0
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	0	0	0
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	0
Other commercial and industrial [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	636	750	674
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	87	194	93
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	549	556	581
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	0
Commercial Real Estate [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	13,615	24,070	10,711
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	8,291	11,548	4,720
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	5,324	12,522	5,991
Troubled Debt Restructuring, Specific allowance	0	162	23
Troubled Debt Restructuring, Charge-offs	0	67
Residential construction and land development [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	7,234	10,083	3,140
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	5,724	1,839	641
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	1,510	8,244	2,499
Troubled Debt Restructuring, Specific allowance	0	162	23
Troubled Debt Restructuring, Charge-offs	0	0
Retail [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	3,543	4,140	3,600
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	1,384	2,584	2,432
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	2,159	1,556	1,168
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	0
Office [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	1,364	5,029	2,324
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	182	3,848	0
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	1,182	1,181	2,324
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	0
Multifamily [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	0	0	0
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	0	0	0
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	0	0	0
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	0
Industrial [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	0	0	0
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	0	0	0
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	0	0	0
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	0
Other commercial real estate [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	1,474	4,818	1,647
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	1,001	3,277	1,647
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	473	1,541	0
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	67
Residential Mortgage [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	22,557	23,266	23,174
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	16,320	16,749	15,049
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	6,237	6,517	8,125
Troubled Debt Restructuring, Specific allowance	102	85	105
Troubled Debt Restructuring, Charge-offs	29	222
Permanent mortage [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	15,680	18,755	16,393
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	11,667	13,117	11,134
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	4,013	5,638	5,259
Troubled Debt Restructuring, Specific allowance	102	85	105
Troubled Debt Restructuring, Charge-offs	5	208
Permanent mortgages guaranteed by US govenment agencies [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	1,579	474	1,597
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	320	181	179
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	1,259	293	1,418
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	0
Permanent mortgages guaranteed by US govenment agencies [Member] | Accruing [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	80,225	55,507	73,985
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	24,483	15,649	17,274
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	55,742	39,858	56,711
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	0	0
Home equity {Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	5,298	4,037	5,184
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	4,333	3,451	3,736
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	965	586	1,448
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	24	14
Consumer [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructuring, Recorded Investment	410	759	419
Troubled Debt Restructuring, Performing in Accordance With Modified Terms	254	583	253
Troubled Debt Restructuring, Not Performing in Accordance With Modified Terms	156	176	166
Troubled Debt Restructuring, Specific allowance	0	0	0
Troubled Debt Restructuring, Charge-offs	$ 4	$ 0