Supplemental Consolidated Financial Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 168,168	$ 161,958	$ 159,818	$ 158,774	$ 147,802	$ 143,324	$ 140,161	$ 134,101	$ 648,718		$ 565,388		$ 461,731
Interest expense	(7,605)	(7,528)	(7,884)	(7,837)	(7,732)	(7,869)	(9,708)	(13,802)	(30,854)		(39,111)		(43,596)
Net interest income	160,563	154,430	151,934	150,937	140,070	135,455	130,453	120,299	617,864		526,277		418,135
Reduction of (provision for) loan losses	(15,014)	(6,788)	(7,999)	(14,529)	(8,245)	(769)	(134)	3,047
Noninterest income	126,688	69,139	80,426	59,293	73,059	95,611	123,708	89,954	335,546		382,332		247,530
Noninterest expense	(143,049)	(135,171)	(135,766)	(132,012)	(134,710)	(127,451)	(121,032)	(117,435)	(545,998)	[1]	(500,628)	[1]	(422,818)	[1]
Income (loss) before income tax expense	129,188	81,610	88,595	63,689	70,174	102,846	132,995	95,865
Income tax expense	29,526	28,470	31,517	23,756	26,284	26,770	43,263	22,770	(113,269)		(119,087)		(61,402)
Net income before noncontrolling interests	99,662	53,140	57,078	39,933	43,890	76,076	89,732	73,095	249,813		282,793		136,817
Comprehensive income attributable to noncontrolling interests	(49,241)	(10,851)	(9,475)	(5,143)	(8,316)	(38,505)	(23,982)	(40,088)	(74,710)		(110,891)		(41,866)
Net income available to common stockholders	$ 50,421	$ 42,289	$ 47,603	$ 34,790	$ 35,574	$ 37,571	$ 65,750	$ 33,007	$ 175,103		$ 171,902		$ 94,951
Earnings per common share—basic	$ 1.13	$ 0.95	$ 1.08	$ 0.79	$ 0.82	$ 0.87	$ 1.53	$ 0.78	$ 3.96		$ 4.00		$ 2.27
Earnings per common share—diluted	$ 1.12	$ 0.94	$ 1.06	$ 0.78	$ 0.81	$ 0.86	$ 1.50	$ 0.76	$ 3.91		$ 3.94		$ 2.24

[1] The Global Commercial Bank segment includes direct depreciation and amortization of $16.3 million, $12.2 million and $9.7 million for 2012, 2011 and 2010, respectively.