Credit Agreement - Interest Expense and Commitment Fees (Details) - Revolving Credit Facility - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Interest expense	$ 9,460	$ 9,294	$ 7,170
Commitment fees	$ 638	$ 1,189	$ 1,359