Incentive Plan (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Nonvested Performance-based Units Activity

Below is a summary of our long-term incentive unit activity for the year ended December 31, 2016.

Unvested Long-term Incentive Units	Units		Weighted-Average Grant Date Fair Value
Unvested, beginning of period	278,301		$	62.85
Granted	29,544		87.18
Vested	(175,975	)	64.35
Cancelled or expired	(3,048	)	54.48
Unvested, end of period	128,822		66.58

Schedule of Share-based Compensation, Performance Based Awards

Level	RMS Relative Market Performance (2014 Awards)	RMS Relative Market Performance (2015 and 2016 Awards)	Market Performance Vesting Percentage
Below Threshold Level	< 0 basis points	< -300 basis points	0	%
Threshold Level	0 basis points	-300 basis points	25	%
Target Level	325 basis points	100 basis points	50	%
High Level	> 650 basis points	> 500 basis points	100	%

Schedule of Share-Based Payment Award Valuation Assumptions

Assumptions used in the valuations are summarized as follows:

Award Date	Expected Stock Price Volatility	Risk-Free Interest Rate
February 11, 2014	33%	0.67%
February 24, 2015	24%	1.00%
January 1, 2016	22%	1.32%
February 16, 2016	26%	0.89%

Summary of Incentive Award Plan Stock Options

The following table summarizes the Amended and Restated 2004 Incentive Award Plan’s stock option activity for the year ended December 31, 2016:

	Year Ended December 31, 2016
	Shares		Weighted average exercise price
Options outstanding, beginning of period	51,622		$	41.04
Exercised	(33,948	)	40.68
Options outstanding, end of period	17,674		$	41.73
Exercisable, end of period	17,674		$	41.73

Summary of Stock Option Outstanding And Exercisable

The following table summarizes information about stock options outstanding and exercisable as of December 31, 2016:

Options outstanding and exercisable
Exercise price	Number outstanding	Weighted average remaining contractual life (years)	Weighted average exercise price		Aggregate intrinsic value
$41.73	17,674	0.33	$	41.73	$	999,111

Schedule of Restricted Stock Activity

Below is a summary of our restricted stock activity for the year ended December 31, 2016.

Unvested Restricted Stock	Shares		Weighted-Average Grant Date Fair Value
Unvested, beginning of period	271,901		$	61.47
Granted (1)	162,685		83.58
Vested	(120,169	)	61.30
Cancelled or expired	(39,775	)	67.22
Unvested, end of period	274,642		73.81

(1) All restricted stock awards granted in 2016 are subject only to service conditions.