Condensed Financial Information of Parent Company (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Condensed Statements of Earnings
Other expense , net									$ (141,025)	$ (168,492)	$ (133,586)
Net earnings	21,712	22,383	21,038	16,600	9,874	17,927	19,015	16,119	81,733	62,935	65,419
Parent Company [Member]
Condensed Statements of Earnings
Excess in net earnings of subsidiaries									20,750	25,278	34,421
Dividends from the bank									68,000	43,100	35,000
Other expense , net									(7,017)	(5,443)	(4,002)
Net earnings									$ 81,733	$ 62,935	$ 65,419