Stock Options, Restricted Stock Units and Employee Stock Purchase Plan - Non-vested Restricted Stock Activity (Details) - Restricted stock units shares in Thousands	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Number of Units
Non-vested shares, beginning balance (in Shares) | shares	888
Granted (in Shares) | shares	6
Vested (in Shares) | shares	0
Forfeited (in Shares) | shares	(10)
Non-vested shares, ending balance (in Shares) | shares	884
Weighted Average Per Share Grant Date Fair Value
Weighted average grant date fair value, beginning balance (in Dollars per share) | $ / shares	$ 32.55
Granted (in Dollars per share) | $ / shares	32.00
Vested (in Dollars per share) | $ / shares	0.00
Forfeited (in Dollars per share) | $ / shares	32.27
Weighted average grant date fair value, ending balance (in Dollars per share) | $ / shares	$ 32.56