Loans Receivable and Credit Quality Loans by Past Due Status (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	$ 4,882,038	$ 4,556,130
Total loans	4,967,607	4,651,228
Financing Receivable Recorded Investment 30 to 59 Days Past Due Still Accruing	4,413	19,020
Financing Receivable Recorded Investment 60 to 89 Days Past Due Still Accruing	5,087	7,937
Financing Receivable Recorded Investment Still Accruing	12,175	26,989
Financing Receivable Recorded Investment Nonaccrual Current Payment Status	49,519	47,157
Financing Receivable Recorded Investment Nonaccrual 30 to 89 Days Past Due	9,992	4,897
Financing Receivable Recorded Investment Nonaccrual Over 89 Days Past Due	13,883	16,055
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	2,675	32
Financing Receivable, Recorded Investment, Nonaccrual Status	73,394	68,109
Commercial and industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	777,390	672,641
Total loans	786,335	678,048
Financing Receivable Recorded Investment 30 to 59 Days Past Due Still Accruing	1,086	1,284
Financing Receivable Recorded Investment 60 to 89 Days Past Due Still Accruing	1,464	364
Financing Receivable Recorded Investment Still Accruing	2,550	1,648
Financing Receivable Recorded Investment Nonaccrual Current Payment Status	4,854	2,866
Financing Receivable Recorded Investment Nonaccrual 30 to 89 Days Past Due	100	566
Financing Receivable Recorded Investment Nonaccrual Over 89 Days Past Due	1,441	327
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Financing Receivable, Recorded Investment, Nonaccrual Status	6,395	3,759
Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	1,757,543	1,630,778
Total loans	1,804,811	1,678,274
Financing Receivable Recorded Investment 30 to 59 Days Past Due Still Accruing	2,445	6,779
Financing Receivable Recorded Investment 60 to 89 Days Past Due Still Accruing	925	2,136
Financing Receivable Recorded Investment Still Accruing	5,995	8,915
Financing Receivable Recorded Investment Nonaccrual Current Payment Status	30,389	32,096
Financing Receivable Recorded Investment Nonaccrual 30 to 89 Days Past Due	4,682	2,310
Financing Receivable Recorded Investment Nonaccrual Over 89 Days Past Due	6,202	4,175
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	2,625	0
Financing Receivable, Recorded Investment, Nonaccrual Status	41,273	38,581
Construction and land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	159,155	145,831
Total loans	164,891	153,709
Financing Receivable Recorded Investment 30 to 59 Days Past Due Still Accruing	25	48
Financing Receivable Recorded Investment 60 to 89 Days Past Due Still Accruing	13	26
Financing Receivable Recorded Investment Still Accruing	88	106
Financing Receivable Recorded Investment Nonaccrual Current Payment Status	4,008	4,825
Financing Receivable Recorded Investment Nonaccrual 30 to 89 Days Past Due	209	172
Financing Receivable Recorded Investment Nonaccrual Over 89 Days Past Due	1,431	2,775
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	50	32
Financing Receivable, Recorded Investment, Nonaccrual Status	5,648	7,772
Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	1,919,345	1,791,483
Total loans	1,941,217	1,823,403
Financing Receivable Recorded Investment 30 to 59 Days Past Due Still Accruing	0	8,997
Financing Receivable Recorded Investment 60 to 89 Days Past Due Still Accruing	2,680	5,410
Financing Receivable Recorded Investment Still Accruing	2,680	14,407
Financing Receivable Recorded Investment Nonaccrual Current Payment Status	9,749	7,236
Financing Receivable Recorded Investment Nonaccrual 30 to 89 Days Past Due	5,000	1,849
Financing Receivable Recorded Investment Nonaccrual Over 89 Days Past Due	4,443	8,428
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Financing Receivable, Recorded Investment, Nonaccrual Status	19,192	17,513
Home equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	127,380	142,018
Total loans	128,252	143,698
Financing Receivable Recorded Investment 30 to 59 Days Past Due Still Accruing	82	1,223
Financing Receivable Recorded Investment 60 to 89 Days Past Due Still Accruing	0	0
Financing Receivable Recorded Investment Still Accruing	82	1,223
Financing Receivable Recorded Investment Nonaccrual Current Payment Status	430	131
Financing Receivable Recorded Investment Nonaccrual 30 to 89 Days Past Due	0	0
Financing Receivable Recorded Investment Nonaccrual Over 89 Days Past Due	360	326
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Financing Receivable, Recorded Investment, Nonaccrual Status	790	457
Consumer and other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	141,225	173,379
Total loans	142,101	174,096
Financing Receivable Recorded Investment 30 to 59 Days Past Due Still Accruing	775	689
Financing Receivable Recorded Investment 60 to 89 Days Past Due Still Accruing	5	1
Financing Receivable Recorded Investment Still Accruing	780	690
Financing Receivable Recorded Investment Nonaccrual Current Payment Status	89	3
Financing Receivable Recorded Investment Nonaccrual 30 to 89 Days Past Due	1	0
Financing Receivable Recorded Investment Nonaccrual Over 89 Days Past Due	6	24
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 96	$ 27