Long-Term Debt - Senior Notes Net Interest Expense (Details) - Senior Notes - 6.125% Senior Notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest Expense and Amortization of Debt Issue Costs
Interest expense	$ 33,687	$ 34,730	$ 5,300
Debt issue cost amortization	1,284	1,282	198
Debt discount amortization	1,111	565	47
Total	$ 36,082	$ 36,577	$ 5,545