Stock-Based Compensation - Performance Stock Units Outstanding Activity (Details) - Performance stock units
9 Months Ended
Sep. 30, 2017
$ / shares
shares
Awards  
Outstanding, beginning of period (in shares) | shares 0
Vested (in shares) | shares 0
Granted (in shares) | shares 193,391
Forfeited (in shares) | shares 0
Outstanding, end of period (in shares) | shares 193,391
Weighted Average Grant-Date Fair Value  
Outstanding, beginning of period (in dollars per share) | $ / shares $ 0.00
Vested (in dollars per share) | $ / shares 0.00
Granted (in dollars per share) | $ / shares 21.53
Forfeited (in dollar per share) | $ / shares 0.00
Outstanding, end of period (in dollars per share) | $ / shares $ 21.53