Fair Value Measurements (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
FINANCIAL ASSETS
Cash and cash equivalents	$ 1,716,052	$ 1,945,148	$ 1,836,954	$ 1,707,733
Securities held for investment	16,099
Loans:
Total loans (net of unearned interest)	3,219,967	3,242,427	3,049,376
Allowance for loan losses	(38,664)	(38,725)	(37,633)
Loans, net	3,181,303	3,203,702	3,011,743
FINANCIAL LIABILITIES
Deposits	5,174,512	5,440,830	5,152,856
Short-term borrowings	4,891	4,571	7,323
Long-term borrowings	11,040	9,178	13,403
Junior subordinated debentures	26,804	26,804	36,083
Carrying Amount [Member]
FINANCIAL ASSETS
Cash and cash equivalents	1,716,052		1,836,954
Securities held for investment	16,099		21,359
Loans:
Total loans (net of unearned interest)	3,219,967		3,049,376
Allowance for loan losses	(38,664)		(37,633)
Loans, net	3,181,303		3,011,743
FINANCIAL LIABILITIES
Deposits	5,174,512		5,152,856
Short-term borrowings	4,891		7,323
Long-term borrowings	11,040		13,403
Junior subordinated debentures	26,804		36,083
Fair Value [Member]
FINANCIAL ASSETS
Cash and cash equivalents	1,716,052		1,836,954
Securities held for investment	16,317		21,788
Loans:
Loans, net	3,240,479		3,047,715
FINANCIAL LIABILITIES
Deposits	5,200,273		5,186,324
Short-term borrowings	4,891		7,323
Long-term borrowings	11,010		13,440
Junior subordinated debentures	31,093		39,289
OFF-BALANCE SHEET FINANCIAL INSTRUMENTS
Loan commitments	1,556		1,197
Letters of credit	$ 469		$ 463

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