Loans Schedule of Accounts, Notes, Loans and Financing Receivables (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	$ 8,813,656,000	$ 6,584,926,000	$ 6,359,419,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	1,007,687,000	506,751,000	502,841,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	2,733,754,000	1,336,447,000	1,329,441,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	1,299,063,000	923,303,000	912,921,000
Loans and Leases Receivable, Gross, Consumer, Revolving, Credit Card	145,113,000	146,387,000	143,918,000
Loans and Leases Receivable, Gross, Consumer, Lease Financing	199,907,000	139,236,000	110,938,000
FDIC Indemnification Asset	69,986,000	113,734,000	131,871,000
Loans	14,269,166,000	9,750,784,000	9,491,349,000
Allowance for loan losses	(143,835,000)	(142,197,000)	(142,586,000)
Net loans	14,125,331,000	9,608,587,000	9,348,763,000
FirstBank Loans	51,900,000	54,200,000	56,000,000
Originated Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	6,420,369,000	5,866,489,000	5,511,678,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	487,283,000	445,211,000	439,062,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	1,647,095,000	1,328,258,000	1,321,081,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	889,372,000	806,078,000	789,743,000
Loans and Leases Receivable, Gross, Consumer, Revolving, Credit Card	145,113,000	146,387,000	143,918,000
Loans and Leases Receivable, Gross, Consumer, Lease Financing	199,907,000	139,236,000	110,938,000
Loans	9,789,139,000	8,731,659,000	8,316,420,000
Allowance for loan losses	(98,291,000)	(98,942,000)	(98,942,000)
Net loans	9,690,848,000	8,632,717,000	8,217,478,000
Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	1,971,062,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	467,608,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	1,080,298,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	306,783,000
Loans	3,825,751,000
Allowance for loan losses	0
Net loans	3,825,751,000
Covered Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	422,225,000	718,437,000	847,741,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	52,796,000	61,540,000	63,779,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	6,361,000	8,189,000	8,360,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	102,908,000	117,225,000	123,178,000
FDIC Indemnification Asset		113,734,000	131,871,000
Loans and Leases Receivable, Gross, Carrying Amount, Covered	654,276,000	1,019,125,000	1,174,929,000
Covered Certain Loans Acquired in Transfer not Accounted for as Debt Securities Allowance for Loan Losses	(45,544,000)	(43,255,000)	(43,644,000)
Net loans	$ 608,732,000	$ 975,870,000	$ 1,131,285,000