Stock-Based Compensation - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		6 Months Ended		12 Months Ended
	Dec. 02, 2013	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Employee stock options
Number of Shares subject to outstanding options
Balance at the beginning of the period (in shares)		5,093,442
Options granted (in shares)		1,553,400	1,356,100
Options forfeited (in shares)		(30,345)
Options exercised (in shares)		(397,270)
Balance at the end of the period (in shares)		6,219,227		5,093,442
Exercisable options (in shares)		2,941,950
Weighted Average Exercise Price (Per Share)
Balance at the beginning of the period (in dollars per share)		$ 15.32
Options granted (in dollars per share)		25.58
Options forfeited (in dollars per share)		21.90
Options exercised (in dollars per share)		7.34
Balance at the end of the period (in dollars per share)		18.36		$ 15.32
Exercisable (in dollars per share)		$ 13.76
Weighted-average remaining contractual life		7 years 10 months 24 days		7 years 7 months 13 days
Weighted-average remaining contractual life of awards exercisable		6 years 9 months 15 days
Aggregate intrinsic value of options outstanding		$ 116,282
Aggregate intrinsic value of options exercisable		$ 68,393
Closing price of common stock (in dollars per share)		$ 37.01
Weighted average fair value of options granted (in dollars per share)		$ 16.86	$ 16.95
The 2010 Plan
Number of Shares subject to outstanding options
Options granted (in shares)	0