Portfolio Loans Not Covered by Loss Share ("Non-covered") - Summary of Recorded Investment in Impaired Non-covered Loans by Category (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2013 loan	Jun. 30, 2013 loan	Jun. 30, 2013 Non-Covered Loans	Dec. 31, 2012 Non-Covered Loans	Jun. 30, 2013 Non-Covered Loans Commercial & Industrial	Dec. 31, 2012 Non-Covered Loans Commercial & Industrial	Jun. 30, 2013 Non-Covered Loans Real Estate Commercial - Investor Owned	Dec. 31, 2012 Non-Covered Loans Real Estate Commercial - Investor Owned	Jun. 30, 2013 Non-Covered Loans Real Estate Commercial - Owner Occupied	Dec. 31, 2012 Non-Covered Loans Real Estate Commercial - Owner Occupied	Jun. 30, 2013 Non-Covered Loans Real Estate Construction and Land Development	Dec. 31, 2012 Non-Covered Loans Real Estate Construction and Land Development	Jun. 30, 2013 Non-Covered Loans Real Estate Residential	Dec. 31, 2012 Non-Covered Loans Real Estate Residential	Jun. 30, 2013 Non-Covered Loans Consumer & Other	Dec. 31, 2012 Non-Covered Loans Consumer & Other	Jun. 30, 2013 Unadvanced Commitment on Impaired Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of loans over 90 days past due and still accruing	0	0
Interest lost on impaired loans	$ 279,000	$ 1,000,000
Impaired Financing Receivable, Interest Income, Cash Basis Method	9,000	24,000
Impaired Financing Receivable, Interest Income, Accrual Method	0
Loans and Leases Receivable, Impaired Loans, Commitment to Lend																	1,728,000
Estimated losses attributable to unadvanced commitments on impaired loans																	259,000
Non-accrual			26,599,000	37,287,000	6,788,000	8,929,000	11,994,000	16,762,000	778,000	5,772,000	4,525,000	3,260,000	2,514,000	2,564,000	0	0
Restructured			0	1,440,000	0	5,000	0	0	0	0	0	1,435,000	0	0	0	0
Loans over 90 days past due and still accruing interest			0	0	0	0	0	0	0	0	0	0	0	0	0	0
Total Recorded Investment			$ 26,599,000	$ 38,727,000	$ 6,788,000	$ 8,934,000	$ 11,994,000	$ 16,762,000	$ 778,000	$ 5,772,000	$ 4,525,000	$ 4,695,000	$ 2,514,000	$ 2,564,000	$ 0	$ 0