Loans and Allowance for Loan Losses (Details 7) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Allowance for loan losses
Balance at beginning of year	$ 273,791	$ 236,574	$ 236,574
Charge-offs	(23,490)	(23,446)	(97,096)
Recoveries	5,412	2,155	14,313
Net (charge-offs) recoveries	(18,078)	(21,291)	(82,783)
Provision for Loan Losses	25,000	40,000	120,000
Balance at end of period	$ 280,713	$ 255,283	$ 273,791