Long-term Debt - Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Credit Agreement [Member]
Debt Instrument [Line Items]
Debt	$ 50,450	$ 0
Senior Notes [Member]
Debt Instrument [Line Items]
Debt	300,000	300,000
Revolving Credit Facility [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Debt	50,450	0
Fair Value, Inputs, Level 2 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	305,630	309,000
Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	$ 50,450	$ 0