Unaudited Quarterly Financial Data Supplemental Consolidated Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 307,333	$ 300,413	$ 293,992	$ 291,658	$ 279,232	$ 264,791	$ 253,926	$ 248,816	$ 1,193,396	$ 1,046,765		$ 891,916
Interest expense	10,728	11,252	10,656	10,237	10,163	10,131	10,155	9,891	42,873	40,340		35,321
Net interest income	296,605	289,161	283,336	281,421	269,069	254,660	243,771	238,925	1,150,523	1,006,425		856,595
Provision for loan losses	7,073	18,950	36,333	33,341	31,261	33,403	26,513	6,452	95,697	97,629		59,486
Noninterest income	113,502	144,140	112,776	86,134	114,506	108,477	126,287	123,524	456,552	472,794		572,239
Noninterest expense	244,567	221,827	200,352	204,033	208,608	184,755	194,112	190,541	870,779	778,016		707,180
Income before income tax expense	158,467	192,524	159,427	130,181	143,706	144,979	149,433	165,456
Income tax expense	54,825	76,877	65,047	53,584	53,697	57,017	54,974	63,066	250,333	228,754		183,508
Net income before noncontrolling interests	103,642	115,647	94,380	76,597	90,009	87,962	94,459	102,390	390,266	374,820	[1],[2]	478,660
Net income attributable to noncontrolling interests	(4,176)	(4,566)	(1,416)	2,577	(2,497)	(6,229)	(8,316)	(13,874)	(7,581)	(30,916)	[1],[3]	(214,790)
Net income available to common stockholders	$ 99,466	$ 111,081	$ 92,964	$ 79,174	$ 87,512	$ 81,733	$ 86,143	$ 88,516	$ 382,685	$ 343,904		$ 263,870
Earnings per common share—basic, in dollars per share	$ 1.91	$ 2.13	$ 1.79	$ 1.53	$ 1.70	$ 1.59	$ 1.68	$ 1.74	$ 7.37	$ 6.70		$ 5.39
Earnings per common share—diluted, in dollars per share	$ 1.89	$ 2.12	$ 1.78	$ 1.52	$ 1.68	$ 1.57	$ 1.66	$ 1.71	$ 7.31	$ 6.62		$ 5.31

[1] During the second quarter of 2015 we adopted new accounting guidance related to our consolidated variable interest entities (ASU 2015-02). Amounts prior to January 1, 2015 have not been revised for the adoption of this guidance. See Note 2— "Summary of Significant Accounting Policies” of the “Notes to the Consolidated Financial Statements” under Part II, Item 8 of this report for additional details.

[2] During the second quarter of 2015 we adopted new accounting guidance related to our consolidated variable interest entities (ASU 2015-02). Amounts prior to January 1, 2015 have not been revised for the adoption of this guidance. See Note 2— "Summary of Significant Accounting Policies” of the “Notes to the Consolidated Financial Statements” under Part II, Item 8 of this report for additional details.

[3] During the second quarter of 2015 we adopted new accounting guidance related to our consolidated variable interest entities (ASU 2015-02). Amounts prior to January 1, 2015 have not been revised for the adoption of this guidance. See Note 2— "Summary of Significant Accounting Policies” of the “Notes to the Consolidated Financial Statements” under Part II, Item 8 of this report for additional details.