Parent Company Only Condensed Financial Information Condensed Statement of Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Interest income	$ 195,384	$ 185,240	$ 177,983	$ 171,014	$ 168,168	$ 161,958	$ 159,818	$ 158,774	$ 729,621	$ 648,718	$ 565,388
Interest expense	(8,386)	(8,144)	(7,902)	(7,845)	(7,605)	(7,528)	(7,884)	(7,837)	(32,277)	(30,854)	(39,111)
Gains on derivative instruments, net									42,184	18,679	36,798
Gains on investment securities, net									419,408	122,114	195,034
Income tax expense	(35,285)	(47,404)	(29,968)	(26,401)	(29,526)	(28,470)	(31,517)	(23,756)	139,058	113,269	119,087
Net income available to common stockholders	58,757	67,621	48,584	40,891	50,421	42,289	47,603	34,790	215,853	175,103	171,902
Parent Company
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Interest income									3,545	3,282	2,819
Interest expense									(24,408)	(23,037)	(27,252)
Dividend income from subsidiary									10,000	0	0
Gains on derivative instruments, net									47,421	17,289	34,654
Gains on investment securities, net									15,238	15,329	16,432
General and administrative expenses									(54,389)	(66,812)	(71,355)
Income tax expense									15,824	(12,200)	(7,468)
Loss before net income of subsidiaries									(18,417)	(41,749)	(37,234)
Net income available to common stockholders									215,853	175,103	171,902
Parent Company | Nonbank Subsidiaries
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Loss before net income of subsidiaries									58,075	21,457	20,013
Equity in undistributed net income of subsidiary									58,075	21,457	20,013
Parent Company | Bank Subsidiaries
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Loss before net income of subsidiaries									186,195	195,395	189,123
Equity in undistributed net income of subsidiary									$ 176,195	$ 195,395	$ 189,123