Long-Term Debt (Interest and Commitment Fee Rates) (Details) - Senior Secured Revolving Credit Facility [Member]	6 Months Ended
	Jun. 30, 2019
Less than 25 percent [Member]
Interest and Commitment Fee Rates [Line Items]
Margin for base rate loans	0.25%
Margin for eurodollar loans	1.25%
Line of Credit Facility, Commitment Fee Percentage	0.375%
Greater than or equal to 25 percent but less than 50 percent [Member]
Interest and Commitment Fee Rates [Line Items]
Margin for base rate loans	0.50%
Margin for eurodollar loans	1.50%
Line of Credit Facility, Commitment Fee Percentage	0.375%
Greater than or equal to 50 percent but less than 75 percent [Member]
Interest and Commitment Fee Rates [Line Items]
Margin for base rate loans	0.75%
Margin for eurodollar loans	1.75%
Line of Credit Facility, Commitment Fee Percentage	0.50%
Greater than or equal to 75 percent but less than 90 percent [Member]
Interest and Commitment Fee Rates [Line Items]
Margin for base rate loans	1.00%
Margin for eurodollar loans	2.00%
Line of Credit Facility, Commitment Fee Percentage	0.50%
Greater than or equal to 90 percent [Member]
Interest and Commitment Fee Rates [Line Items]
Margin for base rate loans	1.25%
Margin for eurodollar loans	2.25%
Line of Credit Facility, Commitment Fee Percentage	0.50%