Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 05, 2017	Feb. 29, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Granted					19,388,000
Special cash dividend paid	$ 140.0
Dividend paid date					May 26, 2017
Dividend payable, date of record					May 17, 2017
Incremental compensation expense			$ 5.6
Weighted-average grant date fair value per share of stock options			$ 0.38	$ 3.73	$ 0.38	$ 3.35
Aggregate intrinsic value of options exercised			$ 0.9	$ 0.6	$ 2.3	$ 2.7
Unrecognized stock-based compensation expense related to nonvested stock awards			$ 6.1		$ 6.1
Weighted average period over which unrecognized stock-based compensation expense is expected to be recognized					2 years 10 months 24 days
Stock Incentive Plan 2011 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for grant (in shares)			2,300,000		2,300,000		2,500,000
Additional common stock available for issuance (in shares)		4,100,000
Number of Options, Granted			19,400,000		19,400,000	3,800,000
Stock Incentive Plan 2011 [Member] | Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period					3 years