Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Loans and Allowance for Loan Losses - Major classifications of loans (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Classifications of loans
Total loans	$ 4,189,368		$ 4,175,008	$ 4,119,235
Less allowance for loan losses	(81,845)		(107,137)	(112,705)
Loans, net	4,107,523		4,067,871	4,006,530
Loans Receivable
Classifications of loans
Total loans	4,189,368		4,175,008	4,119,235
Less allowance for loan losses	(81,845)	(105,753)	(107,137)	(112,705)	(113,601)	(114,468)
Loans, net	4,107,523		4,067,871	4,006,530
Loans Receivable \| Commercial (secured by real estate)
Classifications of loans
Total loans	1,748,145		1,813,365	1,836,477
Less allowance for loan losses	(22,808)		(27,847)	(29,886)		(31,644)
Loans Receivable \| Commercial & industrial
Classifications of loans
Total loans	436,988		458,246	450,222
Less allowance for loan losses	(8,054)		(5,537)	(5,298)		(5,681)
Loans Receivable \| Commercial construction
Classifications of loans
Total loans	132,562		154,769	169,338
Less allowance for loan losses	(4,275)		(8,389)	(10,337)		(6,097)
Loans Receivable \| Commercial
Classifications of loans
Total loans	2,317,695		2,426,380	2,456,037
Loans Receivable \| Residential mortgage
Classifications of loans
Total loans	1,278,559		1,214,203	1,128,336
Less allowance for loan losses	(20,027)		(26,642)	(26,310)		(29,076)
Loans Receivable \| Residential construction
Classifications of loans
Total loans	331,681		381,677	408,966
Less allowance for loan losses	(17,322)		(26,662)	(29,214)		(30,379)
Loans Receivable \| Consumer installment
Classifications of loans
Total loans	261,433		152,748	125,896
Less allowance for loan losses	$ (2,390)		$ (2,747)	$ (2,570)		$ (2,124)