Summary of Stock-Based Compensation Expense by Type of Award (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 92,819	$ 75,528	$ 45,783
Time-based stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	61,802	62,800	43,078
Performance-based stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	23,260	8,337
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	541	497	555
ESPP share issuances
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	2,155	1,360	694
Other Equity Programs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,946	1,846
Non-employee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 3,115	$ 688	$ 1,456