Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jan. 01, 2018
Income Taxes [Line Items]
Effective income tax rate	23.70%	34.00%	23.30%	34.40%
Reduction in corporate tax rate			21.00%		35.00%
Tax code changes description			The TCJA-17 enacted on December 22, 2017 makes broad and complex changes to the U.S. tax code, including, but not limited to, (1) reducing the U.S. federal corporate tax rate from 35% to 21%; (2) requiring companies to pay a one-time transition tax on certain unrepatriated earnings of foreign subsidiaries; (3) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (4) requiring a current inclusion in U.S. federal taxable income of certain earnings of controlled foreign corporations through the implementation of a territorial tax system; and (5) creating a new limitation on deductible interest expense.
Income tax benefits	$ (54,186,000)	$ (74,992,000)	$ (192,814,000)	$ (286,774,000)	$ 30,000,000
Estimated transition tax obligations					$ 11,300,000
Provisional deferred tax - GILTI			$ 0
Unrecognized tax benefits						$ 1,000,000
Impact of unrecognized tax benefits if recognized						$ 1,000,000
Period of expiration of the statute of limitations for certain jurisdictions			Within the next twelve months
Jurisdictions statutes of limitations expiration period			12 months
Maximum
Income Taxes [Line Items]
Accrued interest and penalties	1,000,000		$ 1,000,000
Foreign and U.S. state and local jurisdictions have statutes of limitations, in years			4 years
Minimum
Income Taxes [Line Items]
Foreign and U.S. state and local jurisdictions have statutes of limitations, in years			3 years
ASU 2016-09
Income Taxes [Line Items]
Unfavorable changes amount due to change in tax rate	1,000,000		$ 8,000,000
Increase (decrease) in provision for income taxes			$ (1,000,000)	$ (9,000,000)
ASU 2016-09 | Maximum
Income Taxes [Line Items]
Increase (decrease) in provision for income taxes	$ 1,000,000	$ 1,000,000