Compensation - Activity Associated with Restricted Stock Units (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value, Delivered units	$ (138,324)	$ (61,595)
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Units, Balance outstanding at beginning of period	929,000	1,063,000	1,261,000
Number of Units, Granted	4,283,000	578,000	567,000
Number of Units, Delivered units	(464,000)	(553,000)	(635,000)
Number of Units, Forfeited units	(270,000)	(159,000)	(130,000)
Number of Units, Balance outstanding at end of period	4,478,000	929,000	1,063,000	1,261,000
Weighted-Average Grant Date Fair Value, Balance outstanding at beginning of period	$ 10.83	$ 9.08	$ 7.17
Weighted-Average Grant Date Fair Value, Granted	4.61	12.05	10.65
Weighted-Average Grant Date Fair Value, Delivered units	10.11	8.59	6.79
Weighted-Average Grant Date Fair Value, Forfeited units	5.99	11.34	8.62
Weighted-Average Grant Date Fair Value, Balance outstanding at end of period	$ 5.25	$ 10.83	$ 9.08	$ 7.17
Weighted-Average Remaining Contractual Term (Years)	2 years 6 months	1 year 9 months	1 year 7 months 17 days	1 year 7 months 9 days
Fair Value, Balance outstanding at beginning of period	$ 10,058	$ 9,651	$ 9,039
Fair Value, Granted	19,764	6,964	6,037
Fair Value, Delivered units	(4,692)	(4,753)	(4,312)
Fair Value, Forfeited units	(1,614)	(1,804)	(1,113)
Fair Value, Balance outstanding at end of period	$ 23,516	$ 10,058	$ 9,651	$ 9,039