Stock-Based Compensation - Restricted Stock Units (Details) - Restricted stock units shares in Thousands	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Shares
Balance (in shares) | shares	389
Granted (in shares) | shares	923
Vested (in shares) | shares	(146)
Canceled/Forfeited (in shares) | shares	(77)
Balance (in shares) | shares	1,089
Weighted Average Grant Date Fair Value
Balance (in dollars per share) | $ / shares	$ 10.38
Granted (in dollars per share) | $ / shares	11.72
Vested (in dollars per share) | $ / shares	13.02
Canceled/Forfeited (in dollars per share) | $ / shares	9.78
Balance (in dollars per share) | $ / shares	$ 11.56