Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 9) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	$ 15,819,252,000	$ 13,507,209,000	$ 15,819,252,000	$ 13,507,209,000	$ 14,818,295,000
Covered Loans Allowance
Balance, beginning of period	42,354,000	61,471,000	44,781,000	64,565,000
Provision for losses	(11,927,000)	13,293,000	(2,035,000)	20,759,000
Reduction in allowance due to loan removals	(6,013,000)	(31,617,000)	(18,332,000)	(42,177,000)
Balance, end of period	24,414,000	43,147,000	24,414,000	43,147,000
Loans on nonaccrual status	76,673,000		76,673,000		99,787,000
Loans 90 days or more past due on accrual status	643,000		643,000		981,000
Covered loans
Covered Loans Allowance
Loans on nonaccrual status	0		0		0
Covered loans 30 to 89 days delinquent	3,100,000		3,100,000		43,400,000
Loans 90 days or more past due on accrual status	89,400,000		89,400,000		112,400,000
Commercial
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	6,773,875,000		6,773,875,000		6,211,353,000
Covered Loans Allowance
Loans on nonaccrual status	11,654,000		11,654,000		9,087,000
Loans 90 days or more past due on accrual status					602,000
Commercial real estate mortgages
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	3,101,169,000	2,424,333,000	3,101,169,000	2,424,333,000	2,829,694,000
Covered Loans Allowance
Loans on nonaccrual status	22,433,000		22,433,000		33,198,000
Residential mortgage
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	4,153,051,000	3,822,630,000	4,153,051,000	3,822,630,000	3,962,205,000
Covered Loans Allowance
Loans on nonaccrual status	10,580,000		10,580,000		9,603,000
Loans 90 days or more past due on accrual status	379,000		379,000		379,000
Fixed
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	1,425,776,000		1,425,776,000		1,465,474,000
Covered Loans Allowance
Loans on nonaccrual status	4,402,000		4,402,000		4,902,000
Loans 90 days or more past due on accrual status	379,000		379,000		379,000
Variable
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	2,727,275,000		2,727,275,000		2,496,731,000
Covered Loans Allowance
Loans on nonaccrual status	6,178,000		6,178,000		4,701,000
Real estate construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	217,808,000	301,829,000	217,808,000	301,829,000	222,780,000
Covered Loans Allowance
Loans on nonaccrual status	25,718,000		25,718,000		40,882,000
Construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	179,180,000		179,180,000		165,615,000
Covered Loans Allowance
Loans on nonaccrual status	11,553,000		11,553,000		15,067,000
Land
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	38,628,000		38,628,000		57,165,000
Covered Loans Allowance
Loans on nonaccrual status	14,165,000		14,165,000		25,815,000
Home equity loans and lines of credit
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	700,681,000	741,270,000	700,681,000	741,270,000	711,750,000
Covered Loans Allowance
Loans on nonaccrual status	6,239,000		6,239,000		6,424,000
Loans 90 days or more past due on accrual status	249,000		249,000
Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	149,438,000	130,200,000	149,438,000	130,200,000	142,793,000
Covered Loans Allowance
Loans on nonaccrual status	24,000		24,000		473,000
Commercial Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	440,000		440,000		437,000
Consumer Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	148,998,000		148,998,000		142,356,000
Covered Loans Allowance
Loans on nonaccrual status	24,000		24,000		473,000
Lease financing
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	723,230,000		723,230,000		737,720,000
Covered Loans Allowance
Loans on nonaccrual status	25,000		25,000		120,000
Loans 90 days or more past due on accrual status	15,000		15,000
Nonclassified
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	15,467,995,000		15,467,995,000		14,415,241,000
Nonclassified | Commercial
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	6,659,653,000		6,659,653,000		6,073,459,000
Nonclassified | Commercial real estate mortgages
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	2,997,653,000		2,997,653,000		2,705,469,000
Nonclassified | Residential mortgage
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	4,108,539,000		4,108,539,000		3,928,719,000
Nonclassified | Fixed
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	1,405,192,000		1,405,192,000		1,449,270,000
Nonclassified | Variable
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	2,703,347,000		2,703,347,000		2,479,449,000
Nonclassified | Real estate construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	161,199,000		161,199,000		146,681,000
Nonclassified | Construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	137,033,000		137,033,000		119,189,000
Nonclassified | Land
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	24,166,000		24,166,000		27,492,000
Nonclassified | Home equity loans and lines of credit
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	671,809,000		671,809,000		685,011,000
Nonclassified | Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	149,062,000		149,062,000		142,099,000
Nonclassified | Commercial Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	440,000		440,000		437,000
Nonclassified | Consumer Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	148,622,000		148,622,000		141,662,000
Nonclassified | Lease financing
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	720,080,000		720,080,000		733,803,000
Classified
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	351,257,000		351,257,000		403,054,000
Classified | Commercial
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	114,222,000		114,222,000		137,894,000
Classified | Commercial real estate mortgages
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	103,516,000		103,516,000		124,225,000
Classified | Residential mortgage
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	44,512,000		44,512,000		33,486,000
Classified | Fixed
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	20,584,000		20,584,000		16,204,000
Classified | Variable
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	23,928,000		23,928,000		17,282,000
Classified | Real estate construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	56,609,000		56,609,000		76,099,000
Classified | Construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	42,147,000		42,147,000		46,426,000
Classified | Land
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	14,462,000		14,462,000		29,673,000
Classified | Home equity loans and lines of credit
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	28,872,000		28,872,000		26,739,000
Classified | Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	376,000		376,000		694,000
Classified | Consumer Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	376,000		376,000		694,000
Classified | Lease financing
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	$ 3,150,000		$ 3,150,000		$ 3,917,000