Debt (Other Provisions) (Details) - New Credit Facility	12 Months Ended
	Dec. 31, 2017 qtr
Line Of Credit Facility [Line Items]
Interest payment description	In the case of Alternate Base Rate loans, interest is payable quarterly in arrears. In the case of Adjusted LIBO Rate borrowings, interest is payable on the last day of each relevant interest period and, in the case of any interest period longer than three months, on each successive date three months after the first day of such interest period
Number of consecutive quarters	4
Minimum
Line Of Credit Facility [Line Items]
Current Ratio covenant	100.00%
Maximum
Line Of Credit Facility [Line Items]
Ratio of debt to EBITDAX	400.00%