Stock Based Compensation - Summary of Expense Related to Share-Based Payments (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 31,800	$ 69,939	[1]	$ 93,297	[1]	$ 63,946	[1]
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation		69,939		93,297		63,946
General and Administrative Expense | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation		43,443		56,400		35,234
General and Administrative Expense | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation		$ 26,496		$ 36,897		$ 28,712

[1] Reflects the impact of the Company's adoption of Accounting Standards Update 2016-18, Statement of Cash Flows (Topic 230), which was adopted by the Company on January 1, 2018 and applied retrospectively to results for 2017. The adoption of Topic 230 resulted in the statement of cash flows presenting the changes in the total of cash, cash equivalents and restricted cash. As a result, the Company will no longer present transfers between cash and cash equivalents and restricted cash in the statement of cash flows.