Summary of Significant Accounting Policies (Details) (USD $)	2 Months Ended	12 Months Ended
	Mar. 05, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounting Policies [Abstract]
Stock issued during period, shares, stock split	4
Cash and Cash Equivalents [Abstract]
Cash on deposit with Federal Reserve Bank		$ 622,152,000	$ 329,390,000
Compensating balances with Federal Reserve Bank		1,057,000	5,000,000
Loans and Leases Receivable Disclosure [Abstract]
Mortgage loans held for sale		66,442,000	53,521,000
Impairment losses		70	0	0
Write-downs of OREO		6,724,000	7,464,000	6,724,000
Federal Home Loan Bank Stock and Federal Reserve Bank Stock [Abstract]
Federal Reserve Bank stock		13,357,000	13,357,000
Federal Home Loan Bank stock		6,687,000	6,807,000
Advertising expense		3,555,000	3,048,000	3,200,000
Share-based Compensation [Abstract]
Stock compensation expense		2,485,000	1,906,000	1,660,000
Tax benefits from stock-based compensation		$ 950,000	$ 728,000	$ 635,000