Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Debt issuance costs	$ 4,592	$ 6,627
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares, outstanding (in shares)	37,258,737	38,837,749
Treasury stock, shares outstanding (in shares)	11,498,350	9,363,166