Allowance for Loan Losses Schedule of Credit Losses on Financing Receivables, Current Period (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance, Covered	$ 47,945	$ 41,070	$ 43,255
Provision for Loan Lease and Other Losses Covered	4,138	5,932
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance, Covered	47,945	41,070	43,255	36,417
Provision for Loan Losses Before Benefit Attributable to FDIC Loss Share Agreements	9,677	10,831
Benefit Attributable to FDIC Loss Share Agreements	(5,539)	(4,899)
Provision for Loan Lease and Other Losses Covered	4,138	5,932
Increase in Indemnification Asset	5,539	4,899
Allowance for Loan and Lease Losses, Write-offs	$ (4,987)	$ (6,178)