Incentive Plan - Summary of Non-Vested Performance Stock Units (Details) - Performance shares	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Number of Preferred Stock Units
Non-vested at beginning of period (in shares) | shares	817,512
Granted during period (in shares) | shares	284,625
Vested during period (in shares) | shares	(358,622)
Forfeited during period (in shares) | shares	(60,530)
Non-vested at end of period (in shares) | shares	682,985
Weighted Average Grant Date, Fair Value Per Share
Non-vested at beginning of period (in dollars per share) | $ / shares	$ 36.33
Granted during period (in dollars per share) | $ / shares	11.66
Vested during period (in dollars per share) | $ / shares	35.37
Forfeited during period (in dollars per share) | $ / shares	28.21
Non-vested at end of period (in dollars per share) | $ / shares	$ 27.27