Senior Debt (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Senior Debt (Table Details) [Abstract]
Senior credit facility, maximum amount	$ 900,000,000	$ 900,000,000
Term loan, maximum facility	225,000,000	225,000,000
Revolving facility, maximum facility	675,000,000	675,000,000
Initial Borrowing in Term Loans	225,000,000
Initial Borrowing in Revolving Debt	100,000,000
Mandatory Excess Cash Flow Pre-Payment	141,000,000		$ 27,000,000
Term loan, amount outstanding	50,300,000	50,300,000	191,800,000
Revolving facility, amount outstanding	70,000,000	70,000,000	0
Letters of credit, amount outstanding	$ 91,100,000	91,100,000
Commitment fee percentage	0.50%
Senior credit facilities, additional amount allowed	$ 250,000,000	250,000,000
Line of Credit Facility, Current Borrowing Capacity	$ 225,000,000	$ 225,000,000
Financial Covenants Ratios (Table Details) [Abstract]
Required consolidated total leverage ratio, maximum	4	4
Actual consolidated total leverage ratio	4.25	4.25
Required consolidated senior secured leverage ratio, maximum	2.5	2.5
Actual consolidated senior secured leverage ratio	0.59	0.59
Required consolidated fixed charge coverage ratio, minimum	1.50	1.50
Actual consolidated fixed charge coverage ratio	1.37	1.37
Covenants [Abstract]
Covenants for senior credit facilities - amount available under restricted payment basket	$ 20,000,000	$ 20,000,000
Consolidated funded debt outstanding	629,900,000	629,900,000
Consolidated EBITDA		148,100,000
Outstanding indebtedness less cash in excess of	25,000,000	25,000,000
Consolidated senior secured debt outstanding	$ 87,100,000	87,100,000
Adjusted consolidated EBITDA		375,100,000
Consolidated fixed charges		$ 273,300,000
Event of default-3rd party ownership % of our voting stock	35.00%	35.00%
Event of default-not satisfied or bonded judgment in excess of	$ 50,000,000	$ 50,000,000
Maximum period allowed for pending judgment to satisfy or bond (in days)	30	30
Unsecured line of credit, maximum facility	$ 20,000,000	$ 20,000,000
Unsecured line of credit, amount outstanding	0	0
Maturities of Long-term Debt [Abstract]
2017	1,687,000	1,687,000
2018	2,250,000	2,250,000
2019	72,250,000	72,250,000
2020	2,250,000	2,250,000
2021	41,813,000	41,813,000
Thereafter	0	0
Total senior debt	120,250,000	120,250,000
Dividend declared [Member]
Covenants [Abstract]
Waiver restrictions	4,300,000	4,300,000
Dividend paid [Member]
Covenants [Abstract]
Waiver restrictions	4,300,000	4,300,000
Dividend annual limit [Member]
Covenants [Abstract]
Waiver restrictions	$ 15,000,000	15,000,000
Minimum [Member]
Senior Debt (Table Details) [Abstract]
Commitment fee percentage	0.30%
Maximum [Member]
Senior Debt (Table Details) [Abstract]
Commitment fee percentage	0.50%
Prime Rate [Member]
Senior Debt (Table Details) [Abstract]
Description of variable rate basis	prime
Eurodollar [Member]
Senior Debt (Table Details) [Abstract]
Description of variable rate basis	Eurodollar rate
Line of Credit [Member]
Senior Debt (Table Details) [Abstract]
Maturity date	Aug. 21, 2017
Covenants [Abstract]
Unsecured line of credit, amount outstanding	$ 0	0
Maturities of Long-term Debt [Abstract]
2017	0	0
2018	0	0
2019	0	0
2020	0	0
2021	0	0
Thereafter	$ 0	0
Revolving Credit Facility [Member]
Senior Debt (Table Details) [Abstract]
Maturity date	Mar. 19, 2019
Revolving facility, amount outstanding	$ 70,000,000	70,000,000
Unamortized Debt Issuance Expense	4,700,000	4,700,000	$ 5,100,000
Maturities of Long-term Debt [Abstract]
2017	0	0
2018	0	0
2019	70,000,000	70,000,000
2020	0	0
2021	0	0
Thereafter	$ 0	$ 0
Revolving Credit Facility [Member] | Prime Rate [Member]
Senior Debt (Table Details) [Abstract]
Margin on Prime Rate, actual	1.75%	1.75%
Revolving Credit Facility [Member] | Prime Rate [Member] | Minimum [Member]
Senior Debt (Table Details) [Abstract]
Basis margin on variable rate	0.50%
Revolving Credit Facility [Member] | Prime Rate [Member] | Maximum [Member]
Senior Debt (Table Details) [Abstract]
Basis margin on variable rate	1.75%
Revolving Credit Facility [Member] | Eurodollar [Member]
Senior Debt (Table Details) [Abstract]
Margin on Eurodollar rate, actual	2.75%	2.75%
Revolving Credit Facility [Member] | Eurodollar [Member] | Minimum [Member]
Senior Debt (Table Details) [Abstract]
Basis margin on variable rate	1.50%
Revolving Credit Facility [Member] | Eurodollar [Member] | Maximum [Member]
Senior Debt (Table Details) [Abstract]
Basis margin on variable rate	2.75%
Term Loan [Member]
Senior Debt (Table Details) [Abstract]
Maturity date	Mar. 19, 2021
Term Loan, Periodic Payment, Principal	$ 562,500
Term loan, amount outstanding	$ 50,250,000	$ 50,250,000
Margin on Eurodollar rate, actual	3.00%	3.00%
Margin on Prime Rate, actual	2.00%	2.00%
Maturities of Long-term Debt [Abstract]
2017	$ 1,687,000	$ 1,687,000
2018	2,250,000	2,250,000
2019	2,250,000	2,250,000
2020	2,250,000	2,250,000
2021	41,813,000	41,813,000
Thereafter	$ 0	$ 0