Stock-Based Compensation - Summary of Changes in Number of Shares of Restricted Stock and Restricted Stock Units (Details) shares in Thousands	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Shares
Shares outstanding, beginning of period (in shares) | shares	174
Granted (in shares) | shares	164
Vested (in shares) | shares	(112)
Canceled (in shares) | shares	(28)
Shares outstanding, end of period (in shares) | shares	198
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, beginning of period (in dollars per share) | $ / shares	$ 190.73
Weighted average grant date fair value, granted (in dollars per share) | $ / shares	235.43
Weighted average grant date fair value, vested (in dollars per share) | $ / shares	200.29
Weighted average grant date fair value, canceled (in dollars per share) | $ / shares	218.58
Weighted average grant date fair value, end of period (in dollars per share) | $ / shares	$ 233.20