Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details) (USD $)	Jun. 30, 2012 state	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010
Accounts notes and loans receivable
Loans and leases, excluding covered loans	$ 13,507,209,000		$ 12,309,385,000	$ 11,663,123,000
Less: Allowance for loan and lease losses	(269,534,000)	(266,077,000)	(262,557,000)	(265,933,000)	(263,356,000)	(257,007,000)
Loans and leases, excluding covered loans, net	13,237,675,000		12,046,828,000
Covered loans	1,260,135,000		1,481,854,000
Less: Allowance for loan losses	(43,147,000)	(61,471,000)	(64,565,000)	(67,629,000)	(82,016,000)	(67,389,000)
Covered loans, net	1,216,988,000		1,417,289,000
Total loans and leases	14,767,344,000		13,791,239,000
Net loans and leases	14,454,663,000		13,464,117,000
Unamortized fees, net of deferred costs	5,000,000		7,500,000
Number of states with largest concentration within covered loan portfolio	5
California
Accounts notes and loans receivable
Percent of total loans excluding covered loans outstanding	81.00%
Percent of total covered loans	39.00%
Nevada
Accounts notes and loans receivable
Percent of total loans excluding covered loans outstanding	3.00%
Percent of total covered loans	8.00%
New York
Accounts notes and loans receivable
Percent of total loans excluding covered loans outstanding	7.00%
Texas
Accounts notes and loans receivable
Percent of total covered loans	12.00%
Arizona
Accounts notes and loans receivable
Percent of total covered loans	4.00%
Ohio
Accounts notes and loans receivable
Percent of total covered loans	4.00%
Other states
Accounts notes and loans receivable
Percent of total loans excluding covered loans outstanding	9.00%
Percent of total covered loans	33.00%
Commercial
Accounts notes and loans receivable
Loans and leases, excluding covered loans	5,379,489,000		4,846,594,000
Covered loans	22,772,000		30,911,000
Commercial real estate mortgages
Accounts notes and loans receivable
Loans and leases, excluding covered loans	2,424,333,000		2,110,749,000	1,930,269,000
Less: Allowance for loan and lease losses	(47,648,000)	(46,586,000)	(45,967,000)	(49,060,000)	(47,519,000)	(52,516,000)
Covered loans	1,135,071,000		1,288,352,000
Residential mortgage
Accounts notes and loans receivable
Loans and leases, excluding covered loans	3,822,630,000		3,763,218,000	3,710,765,000
Less: Allowance for loan and lease losses	(12,414,000)	(13,803,000)	(14,029,000)	(12,873,000)	(13,527,000)	(16,753,000)
Covered loans	5,766,000		14,931,000
Real estate construction
Accounts notes and loans receivable
Loans and leases, excluding covered loans	301,829,000		315,609,000	355,014,000
Less: Allowance for loan and lease losses	(17,583,000)	(22,096,000)	(23,347,000)	(29,455,000)	(36,693,000)	(40,824,000)
Covered loans	90,196,000		140,992,000
Equity lines of credit
Accounts notes and loans receivable
Loans and leases, excluding covered loans	741,270,000		741,081,000	735,899,000
Less: Allowance for loan and lease losses	(7,610,000)	(8,032,000)	(8,024,000)	(6,668,000)	(6,445,000)	(7,229,000)
Covered loans	5,265,000		5,167,000
Installment loan
Accounts notes and loans receivable
Loans and leases, excluding covered loans	130,200,000		132,647,000	130,924,000
Less: Allowance for loan and lease losses	(1,764,000)	(1,938,000)	(1,959,000)	(1,951,000)	(5,445,000)	(3,931,000)
Covered loans	1,065,000		1,501,000
Lease financing
Accounts notes and loans receivable
Loans and leases, excluding covered loans	$ 707,458,000		$ 399,487,000