Long-Term Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Disclosure [Abstract]
Coupon interest at 3.75%	$ 3,047	$ 3,047	$ 9,141	$ 9,141
Amortization of debt issuance costs	356	356	1,068	1,068
Total interest expense on Notes	$ 3,403	$ 3,403	$ 10,209	$ 10,209
Coupon interest rate	3.75%		3.75%