Stockholders' Equity and EPS - Reconciliation of Basic EPS to Diluted EPS (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Numerator:
Net income available to common stockholders	[1]	$ 81,733	$ 63,977	$ 256,392	[2]	$ 205,880
Denominator:
Weighted average common shares outstanding-basic (in shares)		51,479	50,752	51,254		48,281
Denominator for diluted calculation (in shares)		52,048	51,571	51,878		49,200
Earnings per common share:
Basic (dollars per share)	[1]	$ 1.59	$ 1.26	$ 5.00	[2]	$ 4.26
Diluted (dollars per share)		$ 1.57	$ 1.24	$ 4.94	[2]	$ 4.18
Stock options and ESPP
Denominator:
Weighted average effect of dilutive securities (in shares)		382	534	411		580
Restricted stock units
Denominator:
Weighted average effect of dilutive securities (in shares)		187	285	213		339

[1] Prior period amounts have been revised to reflect the retrospective application of new accounting guidance adopted in the first quarter of 2015 related to our investments in qualified affordable housing projects (ASU 2014-01). See Note 1— "Basis of Presentation" of the "Notes to Interim Consolidated Financial Statements" under Part I, Item 1 in this report.

[2] Amounts for the nine months ended September 30, 2015, have been revised to reflect the retrospective application of new accounting guidance adopted in the second quarter of 2015 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 1— "Basis of Presentation” of the “Notes to Interim Consolidated Financial Statements (unaudited)” under Part I, Item 1 of this report for additional details.