Allowance for Loan Losses Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary of Activity in the Allowance for Covered Loan Losses) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Allowance for Covered Loan Losses [Roll Forward]
Balance at beginning of period	$ 12,977	$ 0
Provision for covered loan losses before benefit attributable to FDIC loss share agreements	20,282	23,275
Benefit attributable to FDIC loss share agreements	(16,258)	(18,620)
Net provision for covered loan losses	4,024	4,655
Increase in FDIC indemnification asset	16,258	18,618
Loans charged-off	(19,921)	(10,298)
Recoveries of loans charged-off	116	2
Net charge-offs	(19,805)	(10,296)
Balance at end of period	$ 13,454	$ 12,977