Debt - Long-Term Debt (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Feb. 12, 2019	May 23, 2016
Long-term debt
Total credit facility	$ 300,000
Amount available	147,000		$ 198,500
Long-term Line of Credit, Noncurrent	151,200		99,700
Letters of Credit Outstanding, Amount	1,800		1,800
Amortization of Debt Issuance Costs	42	$ 36
Line of Credit | Revolving Credit Facility Due 2024
Long-term debt
Total credit facility			$ 300,000	$ 300,000	$ 300,000
Line of Credit Facility Contingent Increase to Maximum Borrowing Capacity				$ 150,000
Long-term Line of Credit, Noncurrent	$ 151,200
Weighted-average interest rate	2.78%		3.25%
Commitment fee percentage per annum	0.23%		0.23%
Line of Credit | Revolving Credit Facility [Member]
Long-term debt
Long-term Line of Credit, Noncurrent			$ 99,700