Stock Based Compensation - Summary of Expense Related to Share-Based Payments (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 31,800	$ 93,297	$ 63,946	$ 90,122
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation		93,297	63,946	90,122
General and Administrative Expense | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation		56,400	35,234	44,260
General and Administrative Expense | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation		$ 36,897	$ 28,712	$ 45,862