Unaudited Quarterly Financial Data Supplemental Consolidated Financial Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 243,725	$ 229,326	$ 213,841	$ 205,024	$ 195,384	$ 185,240	$ 177,983	$ 171,014	$ 891,916		$ 729,621		$ 648,718
Interest expense	(8,988)	(8,761)	(8,876)	(8,696)	(8,386)	(8,144)	(7,902)	(7,845)	(35,321)		(32,277)		(30,854)
Net interest income	234,737	220,565	204,965	196,328	186,998	177,096	170,081	163,169	856,595		697,344		617,864
Provision for loan losses	(40,435)	(16,610)	(1,947)	(494)	(28,670)	(10,638)	(18,572)	(5,813)	(59,486)		(63,693)		(44,330)
Noninterest income	167,637	80,167	14,210	310,225	238,713	257,650	98,239	78,604	572,239		673,206		335,546
Noninterest expense	(189,000)	(181,989)	(173,446)	(172,436)	(168,850)	(160,524)	(143,292)	(149,014)	(716,871)	[1]	(621,680)	[1]	(545,998)	[1]
Income (loss) before income tax expense	172,939	102,133	43,782	333,623	228,191	263,584	106,456	86,946
Income tax expense	42,302	38,961	33,582	58,917	35,285	47,404	29,968	26,401	(173,762)		(139,058)		(113,269)
Net income before noncontrolling interests	130,637	63,172	10,200	274,706	192,906	216,180	76,488	60,545	478,715		546,119		249,813
Comprehensive income attributable to noncontrolling interests	(71,805)	(177)	40,597	(183,405)	(134,149)	(148,559)	(27,904)	(19,654)	(214,790)		(330,266)		(74,710)
Net income available to common stockholders	$ 58,832	$ 62,995	$ 50,797	$ 91,301	$ 58,757	$ 67,621	$ 48,584	$ 40,891	$ 263,925		$ 215,853		$ 175,103
Earnings per common share—basic, in dollars per share	$ 1.16	$ 1.24	$ 1.05	$ 1.99	$ 1.29	$ 1.48	$ 1.08	$ 0.91	$ 5.39		$ 4.76		$ 3.96
Earnings per common share—diluted, in dollars per share	$ 1.14	$ 1.22	$ 1.04	$ 1.95	$ 1.27	$ 1.46	$ 1.06	$ 0.90	$ 5.31		$ 4.70		$ 3.91

[1] The Global Commercial Bank segment includes direct depreciation and amortization of $20.9 million, $18.7 million and $14.4 million for 2014, 2013 and 2012, respectively.