Segment Reporting - Additional Information (Detail) (USD $)	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
Segment Reporting Information [Line Items]
Noninterest income	$ 73,059,000	$ 95,611,000	$ 123,708,000	$ 89,954,000	$ 71,864,000	$ 86,236,000	$ 40,157,000	$ 49,273,000	$ 382,332,000	$ 247,530,000	$ 97,743,000
Sale of Certain Available For Sale Securities
Segment Reporting Information [Line Items]
Noninterest income									37,300,000	24,700,000
Global Commercial Bank
Segment Reporting Information [Line Items]
Certain changes to the items reported, effect on income before income tax expense										$ 39,700,000	$ 31,800,000