Share-based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions		4 Months Ended	6 Months Ended	8 Months Ended	12 Months Ended
	Apr. 21, 2015	Apr. 15, 2015	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation.
Amortization expense for capitalized software					$ 9.6	$ 10.4	$ 11.0
Non-voting common interest units outstanding				15,394,426	15,394,426
Forfeited or expired (in shares)					(234,000)
Outstanding (in shares)				8,994,000	8,994,000
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	6 months
Weighted average risk free interest rate (as a percent)					0.72%	0.12%	0.10%
Expected stock price volatility (as a percent)					47.00%	25.00%	25.00%
Class A-2 profits interests
Share-based Compensation.
Expense recognized					$ 1.5	$ 16.0	$ 13.4
Unrecognized share-based compensation expense				$ 2.2	$ 2.2
Weighted average period for compensation expense expected to be recognized					1 year 7 months 6 days
Activity
Outstanding (in shares)		6,069,007	6,069,007		6,069,007	4,434,452
Granted (in shares)		6,418				1,992,556
Repurchased (in shares)		(13,495)				(358,001)
Outstanding (in shares)		6,061,930				6,069,007	4,434,452
Weighted Average Fair Value
Outstanding (in dollars per share)		$ 6.82	$ 6.82		$ 6.82	$ 6.82
Granted (in dollars per share)		7.52				7.52
Repurchased (in dollars per share)		7.17				6.51
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	3 years 4 months 24 days
Weighted average remaining contractual life, granted		3 years
Class A-2 profits interests | Maximum
Share-based Compensation.
Vesting period					4 years	4 years	4 years
Class B interests | East MIP
Share-based Compensation.
One time expense recognized					$ 41.4
Additional expense recognized					3.5
Expense recognized					44.9	$ 0.0
Unrecognized share-based compensation expense				$ 2.1	$ 2.1
Weighted average period for compensation expense expected to be recognized					1 year 9 months 18 days
Capitalized software development costs					$ 9.2
Amortization expense for capitalized software					$ 8.5
Class B interests | East MIP | Time based vesting
Share-based Compensation.
Vesting period					4 years	4 years
Number of interests vested			0			0
Class A | 2015 Management Incentive Plan
Share-based Compensation.
Granted (in shares)				576,693
Non-qualified stock options
Share-based Compensation.
Granted (in shares)					9,228,000
Weighted Average Exercise Price Per Share
Granted (in dollars per share)					$ 19.00
Forfeited or expired (in dollars per share)					19.00
Outstanding (in dollars per share)				$ 19.00	$ 19.00
Weighted Average Remaining Life, outstanding
Weighted Average Remaining Life					9 years 3 months 15 days
Weighted average remaining contractual life, granted					10 years
Non-qualified stock options | 2015 Management Incentive Plan
Share-based Compensation.
Vesting period	4 years
Expiration period	10 years
Expense recognized					$ 4.7
Unrecognized share-based compensation expense				$ 22.4	$ 22.4
Weighted average period for compensation expense expected to be recognized					3 years 3 months 18 days
Granted (in shares)	9,228,000
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
Restricted stock units
Share-based Compensation.
Unrecognized share-based compensation expense				$ 20.9	$ 20.9
Weighted average period for compensation expense expected to be recognized					3 years
Activity
Granted (in shares)					984,466
Outstanding (in shares)				984,466	984,466
Weighted Average Fair Value
Granted (in dollars per share)					$ 22.32
Outstanding (in dollars per share)				$ 22.32	$ 22.32
Restricted stock units | 2015 Management Incentive Plan
Share-based Compensation.
Vesting period				4 years
Activity
Granted (in shares)				984,466
Restricted stock units | Class A
Share-based Compensation.
Expense recognized					$ 13.7
Restricted stock units | Class A | 2015 Management Incentive Plan
Share-based Compensation.
Time period used for the volume weighted average price to determine fair value				3 days