Share-based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands			4 Months Ended	12 Months Ended			20 Months Ended
	Apr. 21, 2015	Apr. 15, 2015	Apr. 15, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Share-based Compensation.
Non-voting common interest units outstanding				14,231,535	15,394,426		14,231,535
Number of non-voting common interest units forfeited or repurchased				1,162,891	57,106
Class A
Share-based Compensation.
Expense recognized				$ 10,600	$ 13,200
Class A-2 profits interests and Class B interests | East MIP
Weighted-average assumptions used in estimating grant date fair values
Expected life (in years)					2 years 8 months 12 days	6 months
Weighted average risk free interest rate (as a percent)					0.72%	0.12%
Expected stock price volatility (as a percent)					47.00%	25.00%
Class A-2 profits interests
Activity
Outstanding (in shares)				6,069,007
Granted (in shares)			6,418
Repurchased (in shares)			(13,495)
Outstanding (in shares)		6,061,930	6,061,930		6,069,007
Weighted Average Fair Value
Outstanding (in dollars per share)				$ 6.82
Granted (in dollars per share)			$ 7.52
Forfeited (in dollars per share)			7.17
Outstanding (in dollars per share)		$ 6.82	$ 6.82		$ 6.82
Weighted Average Remaining Life, outstanding
Weighted Average Remaining Life			2 years 3 months 7 days		2 years 6 months 15 days
Weighted average remaining contractual life, granted			3 years
Non-voting common interest units (formerly Class B interests)
Share-based Compensation.
Expense recognized				$ 1,100	$ 44,900
Unrecognized share-based compensation expense				$ 800	$ 2,100		$ 800
Weighted average period for compensation expense expected to be recognized				1 year	1 year 9 months 18 days
Capitalized software development costs				$ 90	$ 9,200
Non-voting common interest units (formerly Class B interests) | East MIP
Share-based Compensation.
Amortization expense related to share based compensation				700	8,500
Non-voting common interest units (formerly Class A 2 profits interests)
Share-based Compensation.
Expense recognized				1,300	1,500	$ 16,000
Unrecognized share-based compensation expense				$ 800	$ 2,500		800
Weighted average period for compensation expense expected to be recognized				9 months 18 days	1 year 7 months 6 days
Non-voting common interest units (formerly Class A 2 profits interests) | Maximum
Share-based Compensation.
Vesting period		4 years
Non-qualified stock options | 2015 Management Incentive Plan
Share-based Compensation.
Vesting period	4 years
Expiration period	10 years
Expense recognized				$ 5,600	$ 4,700
Unrecognized share-based compensation expense				$ 14,200	$ 22,400		$ 14,200
Weighted average period for compensation expense expected to be recognized				2 years 3 months 18 days	3 years 3 months 18 days
Forfeited or repurchased (in shares)				760,000	234,000
Outstanding (in shares)				8,994,000
Granted (in shares)					9,228,000
Forfeited or expired (in shares)				(760,000)	(234,000)
Outstanding (in shares)				8,234,000	8,994,000		8,234,000
Weighted Average Exercise Price Per Share
Outstanding (in dollars per share)				$ 19.00
Granted (in dollars per share)					$ 19.00
Outstanding (in dollars per share)				$ 19.00	$ 19.00		$ 19.00
Weighted-average assumptions used in estimating grant date fair values
Expected life (in years)					6 years 3 months
Weighted average risk free interest rate (as a percent)					1.52%
Expected stock price volatility (as a percent)					30.00%
Expected dividend yield (as a percent)					5.05%
Weighted Average Fair Value
Granted (in dollars per share)					$ 3.02
Weighted Average Remaining Life, outstanding
Weighted Average Remaining Life				8 years 3 months 15 days	9 years 3 months 15 days
Weighted average remaining contractual life, granted					10 years
Options Exercisable, Number of Options (in shares)				2,058,500			2,058,500
Options Exercisable, Weighted Average Exercise Price (in dollars per share)				$ 19.00			$ 19.00
Restricted stock units
Share-based Compensation.
Unrecognized share-based compensation expense				$ 28,500	$ 20,900		$ 28,500
Weighted average period for compensation expense expected to be recognized				2 years 7 months 6 days	3 years
Restricted stock units | Class A
Share-based Compensation.
Expense recognized				$ 6,300	$ 500
Restricted stock units | 2015 Management Incentive Plan
Activity
Outstanding (in shares)				984,466
Granted (in shares)				1,019,148	984,466
Forfeited (in shares)				(133,138)
Vested (in shares)				(297,035)
Outstanding (in shares)				1,573,441	984,466		1,573,441
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding (in dollars per share)				$ 22.32
Granted (in dollars per share)				16.06	$ 22.32
Forfeited (in dollars per share)				22.51
Vested (in dollars per share)				16.48
Outstanding (in dollars per share)				$ 18.28	$ 22.32		$ 18.28
Restricted stock units | 2015 Management Incentive Plan | Maximum
Share-based Compensation.
Vesting period							4 years