Stock-Based Compensation - Summary of Changes in Number of Shares of Restricted Stock and Restricted Stock Units (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Shares
Shares outstanding, beginning of period (in shares) | shares	379
Granted (in shares) | shares	204
Vested (in shares) | shares	(204)
Canceled (in shares) | shares	(48)
Shares outstanding, end of period (in shares) | shares	331
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, beginning of period (in dollars per share) | $ / shares	$ 140.39
Weighted average grant date fair value, granted (in dollars per share) | $ / shares	149.95
Weighted average grant date fair value, vested (in dollars per share) | $ / shares	136.85
Weighted average grant date fair value, canceled (in dollars per share) | $ / shares	153.24
Weighted average grant date fair value, end of period (in dollars per share) | $ / shares	$ 149.24