Income Taxes Components of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Current provision:
Federal									$ 191,194		$ 181,011		$ 105,616
State									50,815		45,488		26,204
Deferred expense (benefit):
Federal									(11,270)		(36,067)		11,960
State									(1,985)		(6,924)		3,050
Income tax expense	$ 53,697	$ 57,017	$ 54,974	$ 63,066	$ 46,077	$ 40,207	$ 35,928	$ 61,296	$ 228,754	[1]	$ 183,508	[1]	$ 146,830	[1]

[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 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.