Incentive Plan - Summary of Stock Options Outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Number of Options Granted
Outstanding, beginning of period (in shares)	654,016
Options granted (in shares)	0
Options forfeited (in shares)	(17,266)
Options exercised (in shares)	0	0
Outstanding, end of period (in shares)	636,750
Exercisable, end of period, number of options granted (in shares)	222,354
Vested or expected to vest, end of period, number of options granted (in shares)	414,396
Weighted Average Exercise Price
Outstanding, beginning of period (dollars per share)	$ 39.23
Options granted (dollars per share)	0
Options forfeited (dollars per share)	39.23
Options exercised (dollars per share)	0
Outstanding, end of period (dollars per share)	39.23
Exercisable, end of period (dollars per share)	39.23
Vested or expected to vest, end of period (dollars per share)	$ 39.23
Weighted Average Remaining Contractual Term
Outstanding, end of period	8 years 7 months 6 days
Exercisable, end of period	8 years 7 months 6 days
Vested or expected to vest, end of period	8 years 7 months 6 days
Aggregate Intrinsic Value
Outstanding, end of period	$ 0
Exercisable, end of period	0
Vested or expected to vest, end of period	$ 0