Business, Basis of Presentation and Summary of Significant Accounting Policies - Initial and Secondary Public Offerings (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands					12 Months Ended
	Dec. 14, 2017	Jun. 07, 2017	Feb. 28, 2017	Jun. 01, 2016	Apr. 30, 2017
Initial and Secondary Public Offerings
Net proceeds from initial public offering				$ 156,900	$ 156,941
Second Lien Term Loan
Initial and Secondary Public Offerings
Loan repayment				$ 160,000	$ 160,000
Initial public offering | Common Stock
Initial and Secondary Public Offerings
Number of shares issued				8,100	8,050
Offering price (in dollars per share)				$ 21.00
Underwriters over-allotment option | Common Stock
Initial and Secondary Public Offerings
Number of shares issued				1,100
Selling stockholders
Initial and Secondary Public Offerings
Shares sold	5,000
Price to the public (in dollars per share)	$ 38.25
Selling stockholders | Secondary offering
Initial and Secondary Public Offerings
Shares sold		5,800	8,000
Price to the public (in dollars per share)		$ 33.00	$ 29.25
Selling stockholders | Underwriters over-allotment option
Initial and Secondary Public Offerings
Shares sold		800	1,000