Stock-Based Compensation (Assump) (Details) - $ / shares	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Summary of weighted average assumptions used to value options granted
Grant date fair value of options (in dollars per share)	$ 13.26	$ 14.51	$ 9.49
Volatility (as a percent)	42.40%	43.80%	42.20%
Risk-free interest rate (as a percent)	1.40%	2.10%	1.40%
Expected term (in years)	6 years 2 months 12 days	6 years 3 months 18 days	6 years 3 months 18 days