Employee Incentive Programs (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Series B Unit Activity

A summary of the Series B Unit activity for the years ended December 31, 2017, 2016 and 2015 is presented below.

	Number of Series B Units			Weighted Average Estimated Fair Value per Unit
Non-vested at December 31, 2014		642,355		$	21.04
Vested		(175,196	)		20.43
Forfeited or cancelled		(92,500	)		22.08
Non-vested at December 31, 2015		374,659		$	21.07
Granted		147,000			4.11
Vested		(122,455	)		17.95
Forfeited or cancelled		(72,750	)		21.22
Non-vested at December 31, 2016		326,454		$	14.57
Granted		35,100			20.99
Vested		(104,614	)		17.16
Forfeited or cancelled		(22,500	)		15.10
Non-vested at December 31, 2017		234,440		$	14.32

Summary of Fair Value Grant Estimated Using Weighted Average Assumptions

The fair value of each grant was estimated at the date of grant using the following weighted-average assumptions:

	2017 Grants			2016 Grants
Assumed value of equity (in thousands)	$	789,426		$	196,280
Risk-free rate of interest		1.16	%		1.11	%
Expected time to a liquidity event (in years)		1			3
Expected volatility of equity		40	%		70	%
Discount for lack of marketability		25	%		34	%