Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) purchase_period $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	May 16, 2013 shares
Stockholders Equity Note [Line Items]
Preferred stock, par value (usd per share) | $ / shares	$ 0.0001	$ 0.0001
Total intrinsic value of stock options exercised | $	$ 18,100	$ 18,200	$ 7,400
Employees’ taxes paid upon the vesting of restricted stock units | $	$ (46,168)	$ (29,857)	$ (20,716)
Employee Stock Purchase Plan, Duration Of Offering Period	24 months
Number of offering periods | purchase_period	4
Number of shares issued (in thousands)	202,000	197,000	230,000
Stock-based compensation expense | $	$ 58,854	$ 54,148	$ 52,943
Stockholder Rights Plan
Stockholders Equity Note [Line Items]
Number of shares called by each right (shares)	0.001
Amended And Restated 2005 Stock Incentive Plan
Stockholders Equity Note [Line Items]
Shares reserved for issuance	6,885,248
2001 Purchase Plan
Stockholders Equity Note [Line Items]
Employee stock purchase plan, purchase price as percentage of fair market value of common stock	85.00%
Restricted Stock Units (RSUs)
Stockholders Equity Note [Line Items]
Vested rand released in period, Total intrinsic value | $	$ 99,500	59,800	45,900
Vested in period, Fair value | $	$ 46,200	$ 39,100	$ 30,000
Granted (usd per share) | $ / shares	$ 118.77	$ 67.82	$ 57.78
Total unamortized compensation cost | $	$ 72,900
Weighted average period of total unamortized cost	2 years 1 month 6 days
Restricted stock units, shares vested and released (shares)	851,693
Restricted stock units, shares withheld for tax payments	287,790
Restricted stock units, net issuance	563,903
Stock Options | Incentive Plan 2005
Stockholders Equity Note [Line Items]
Weighted award against authorized maximum (shares)	25% vesting one year from the date of grant and 1/48th each month thereafter
Market Performance Based Restricted Stock Units
Stockholders Equity Note [Line Items]
Vested rand released in period, Total intrinsic value | $	$ 28,800	$ 17,400	$ 9,200
Vested in period, Fair value | $	$ 15,000	9,900	4,900
Granted (usd per share) | $ / shares	$ 88.80
Total unamortized compensation cost | $	$ 12,200
Weighted average period of total unamortized cost	1 year
Restricted stock units, shares vested and released (shares)	282,548
Restricted stock units, shares withheld for tax payments	118,562
Restricted stock units, net issuance	163,986
Market Performance Based Restricted Stock Units | Minimum
Stockholders Equity Note [Line Items]
Stock incentive plan, vesting period	2 years
Market Performance Based Restricted Stock Units | Maximum
Stockholders Equity Note [Line Items]
Stock incentive plan, vesting period	3 years
Percentage of market-performance based restricted stock units eligible to vest over the vesting period	200.00%
Employee Stock Purchase Plan 2010
Stockholders Equity Note [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Shares Remaining Available For Issuance	735,301
Employee Stock Incentive Plan 2005
Stockholders Equity Note [Line Items]
Number of shares available for grant (shares)				27,783,379
Share-based Compensation Arrangement by Share-based Payment Award, Weight Of Awarded Shares Against Authorized Maximum	1.9			1.5
Employee Stock Purchase Plan 2010 | Maximum
Stockholders Equity Note [Line Items]
Maximum number of shares available	2,400,000
Employee Stock Purchase Plan
Stockholders Equity Note [Line Items]
Total unamortized compensation cost | $	$ 2,700
Weighted average period of total unamortized cost	7 months 6 days
Stock-based compensation expense | $	$ 5,400	$ 2,700	$ 4,100
Monthly Vesting | Stock Options | Incentive Plan 2005
Stockholders Equity Note [Line Items]
Stock incentive plan, vesting percentage	2.08%