Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Statutory U.S. federal rate	35.00%	35.00%	35.00%
Operating loss carryforwards, valuation allowance	$ 68,600,000	$ 88,400,000
Unrecognized tax benefits	131,608,000	152,581,000	$ 47,109,000	$ 59,405,000
Unrecognized tax benefits recognition impact on effective tax rate	128,200,000
Interest on income taxes accrued net of related benefit	21,200,000	20,200,000	7,000,000
Interest on income tax expense net of related tax benefit	2,700,000	$ 5,100,000	$ 1,400,000
Decrease in Unrecognized Tax Benefits is Reasonably Possible	86.2
State and Local Jurisdiction
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Operating loss carryforwards	$ 5,300,000
Minimum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Combination of subsidiaries (in years)	3 years
Maximum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Combination of subsidiaries (in years)	4 years