Nature of Business, Interim Financial Data and Basis of Presentation (Condensed Supplemental Cash Flow) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Supplemental disclosures of cash flow information:
Interest paid			$ 37,428,000	$ 51,575,000
Income taxes (refunded) paid			(2,155,000)	17,138,000
Supplemental disclosures of non-cash flow information:
Revenue	$ 196,385,000	$ 280,808,000	570,321,000	827,977,000
Reconciliation of cash and cash equivalents and restricted cash to the unaudited Condensed Consolidated Balance Sheet:
Cash and cash equivalents	353,722,000	7,751,000	353,722,000	7,751,000	$ 15,142,000
Restricted cash	0	1,392,000	0	1,392,000	1,865,000
Total cash and cash equivalents and restricted cash	353,722,000	9,143,000	353,722,000	9,143,000	$ 17,007,000	$ 30,038,000
Trade
Supplemental disclosures of non-cash flow information:
Revenue	7,200,000	9,400,000	22,154,000	33,388,000
Expense	$ 6,800,000	$ 9,600,000	$ 20,941,000	$ 31,614,000