Income Taxes - Summary of Effective Income Tax Rate (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Expected income taxes		$ 270,282	$ 268,165	$ 274,637
Increase (reduction) in income taxes resulting from, amount:
Low income housing investments		(18,202)	(19,031)	(17,541)
Share-based awards		(18,653)	0	0
Other		(782)	760	(493)
Income tax expense from continuing operations	[1]	$ 232,645	$ 249,894	$ 256,603
Expected income taxes		35.00%	35.00%	35.00%
Increase (reduction) in income taxes resulting from, percent:
Low income housing investments		(2.40%)	(2.50%)	(2.20%)
Share-based awards		(2.40%)	(0.00%)	(0.00%)
Other		(0.10%)	0.10%	0.00%
Income tax expense from continuing operations		30.10%	32.60%	32.80%

[1] Certain current year amounts were prospectively adjusted to give effect to the adoption of ASU 2016-09 related to excess tax benefits from stock compensation as described in Note 1—Significant Accounting Policies under "Accounting Pronouncements Adopted in the Current Year."