Loans Schedule of Accounts, Notes, Loans and Financing Receivables (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	$ 8,778,761,000	$ 6,584,926,000	$ 6,320,009,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	958,877,000	506,751,000	503,919,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	2,725,517,000	1,336,447,000	1,271,712,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	1,274,216,000	923,303,000	896,468,000
FDIC Indemnification Asset	83,910,000	113,734,000	152,615,000
Loans and Leases Receivable, Gross, Consumer, Revolving, Credit Card	142,319,000	146,387,000	142,586,000
Loans and Leases Receivable, Gross, Consumer, Lease Financing	188,353,000	139,236,000	84,507,000
Acquired Loans Total	14,151,953,000	9,750,784,000	9,371,816,000
Allowance for loan losses	(147,714,000)	(142,197,000)	(146,455,000)
Net loans	14,004,239,000	9,608,587,000	9,225,361,000
FirstBank Loans	52,900,000	54,200,000	67,900,000
Originated Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	5,997,812,000	5,866,489,000	5,404,971,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	462,427,000	445,211,000	438,147,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	1,496,663,000	1,328,258,000	1,262,877,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	845,051,000	806,078,000	766,840,000
Loans and Leases Receivable, Gross, Consumer, Revolving, Credit Card	142,319,000	146,387,000	142,586,000
Loans and Leases Receivable, Gross, Consumer, Lease Financing	188,353,000	139,236,000	84,507,000
Acquired Loans Total	9,132,625,000	8,731,659,000	8,099,928,000
Allowance for loan losses	(98,645,000)	(98,942,000)	(103,849,000)
Net loans	9,033,980,000	8,632,717,000	7,996,079,000
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	2,275,243,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	440,394,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	1,221,060,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	322,195,000
Acquired Loans Total	4,258,892,000
Allowance for loan losses	0
Net loans	4,258,892,000
Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	505,706,000	718,437,000	915,038,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	56,056,000	61,540,000	65,772,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	7,794,000	8,189,000	8,835,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	106,970,000	117,225,000	129,628,000
FDIC Indemnification Asset	83,910,000	113,734,000	152,615,000
Net loans	711,367,000	975,870,000	1,229,282,000
Loans and Leases Receivable, Gross, Carrying Amount, Covered	760,436,000	1,019,125,000	1,271,888,000
Covered Certain Loans Acquired in Transfer not Accounted for as Debt Securities Allowance for Loan Losses	$ (49,069,000)	$ (43,255,000)	$ (42,606,000)