Senior Debt (Details)	3 Months Ended
	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Senior Debt (Table Details) [Abstract]
Unamortized Debt Issuance Expense	$ 2,100,000	$ 2,600,000
Letters of credit, amount outstanding	$ 92,000,000
Line of credit commitment fee percentage	0.40%
Line of credit commitment fee	$ 700,000
Senior credit facilities, additional amount allowed	$ 100,000,000
Debt refinancing charges		500,000
Debt arrangement and amendment fees		2,100,000
Financial Covenants Ratios (Table Details) [Abstract]
Required consolidated fixed charge coverage ratio, minimum	1.10
Actual consolidated fixed charge coverage ratio	5.13
Covenants [Abstract]
Adjusted consolidated EBITDA	$ 204,000,000
Consolidated fixed charges	$ 39,700,000
Event of default-3rd party ownership % of our voting stock	35.00%
Event of default-not satisfied or bonded judgment in excess of	$ 50,000,000
Maximum period allowed for pending judgment to satisfy or bond (in days)	30
Minimum [Member]
Senior Debt (Table Details) [Abstract]
Line of credit commitment fee percentage	0.30%
Maximum [Member]
Senior Debt (Table Details) [Abstract]
Line of credit commitment fee percentage	0.50%
Eurodollar [Member]
Senior Debt (Table Details) [Abstract]
Description of variable rate basis	Eurodollar rate
Prime Rate [Member]
Senior Debt (Table Details) [Abstract]
Description of variable rate basis	prime
Revolving Credit Facility [Member]
Senior Debt (Table Details) [Abstract]
Senior credit facility, maximum amount	$ 200,000,000
Revolving facility, amount outstanding	$ 0
Maturity date	Dec. 31, 2019
Covenants [Abstract]
Line of Credit Facility, Remaining Borrowing Capacity	$ 95,100,000
Revolving Credit Facility [Member] | Eurodollar [Member]
Senior Debt (Table Details) [Abstract]
Margin on Eurodollar rate, actual	2.00%
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	3.00%
Revolving Credit Facility [Member] | Prime Rate [Member]
Senior Debt (Table Details) [Abstract]
Margin on Prime Rate, actual	1.00%
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	2.00%
Line of Credit [Member]
Covenants [Abstract]
Unsecured line of credit, maximum facility	$ 12,500,000
Unsecured line of credit, amount outstanding	$ 0	$ 0