Stock Options, Restricted Stock Units and Employee Stock Purchase Plan - Non-vested Restricted Stock Activity (Details) - Restricted stock units shares in Thousands	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Number of Units
Non-vested shares, beginning balance (in Shares) | shares	416
Granted (in Shares) | shares	666
Vested (in Shares) | shares	(138)
Forfeited (in Shares) | shares	(42)
Non-vested shares, ending balance (in Shares) | shares	902
Weighted Average Per Share Grant Date Fair Value
Weighted average grant date fair value, beginning balance (in Dollars per share) | $ / shares	$ 31.52
Granted (in Dollars per share) | $ / shares	33.10
Vested (in Dollars per share) | $ / shares	32.55
Forfeited (in Dollars per share) | $ / shares	31.04
Weighted average grant date fair value, ending balance (in Dollars per share) | $ / shares	$ 32.55