Incentive Plan - Summary of Stock Options (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Number of Options Granted
Outstanding, beginning of period (in shares) | shares	654,016
Options granted (in shares) | shares	0
Options forfeited (in shares) | shares	(34,530)
Options exercised (in shares) | shares	0
Options expired (in shares) | shares	(23,750)
Outstanding, end of period (in shares) | shares	595,736
Exercisable, end of period (in shares) | shares	333,501
Vested or expected to vest, end of period (in shares) | shares	262,235
Weighted Average Exercise Price
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 39.23
Options granted (in dollars per share) | $ / shares	0
Options forfeited (in dollars per share) | $ / shares	39.23
Options exercised (in dollars per share) | $ / shares	0
Options expired (in dollars per share) | $ / shares	39.23
Outstanding, end of period (in dollars per share) | $ / shares	39.23
Exercisable, end of period (in dollars per share) | $ / shares	38.52
Vested or expected to vest, end of period (in dollars per share) | $ / shares	$ 40.12
Weighted Average Remaining Contractual Term (Years)
Outstanding, end of period	8 years 25 days
Exercisable, end of period	8 years 18 days
Vested or expected to vest, end of period	8 years 1 month 6 days
Aggregate Intrinsic Value
Outstanding, end of period | $	$ 0
Exercisable, end of period | $	0
Vested or expected to vest, end of period | $	$ 0