Equity Compensation (Restricted Stock Units) (Details) - Restricted stock units
3 Months Ended
Mar. 31, 2018
$ / shares
shares
Restricted stock units  
Non-vested balance at beginning of period (in shares) 1,290,660
Awarded 326,150
Vested (425,282)
Forfeited (34,250)
Non-vested balance at end of period (in shares) 1,157,278
Weighted Average Grant Date Fair Value  
Non-vested balance at beginning of period (in dollars per share) | $ / shares $ 9.75
Awarded (in dollars per share) | $ / shares 29.21
Vested (in dollars per share) | $ / shares 9.83
Forfeited (in dollars per share) | $ / shares 9.54
Non-vested balance at end of period (in dollars per share) | $ / shares $ 15.21
Shares withheld for tax purposes (in shares) 146,359
Issuance of shares net of shares withheld (in shares) 278,923