Loans Receivable and Credit Quality Loans by Portfolio Segment (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 4,967,607	$ 4,651,228
Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	786,335	678,048
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,804,811	1,678,274
Construction and land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	164,891	153,709
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,941,217	1,823,403
Home equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	128,252	143,698
Consumer and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 142,101	$ 174,096