Money Pool (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Amount outstanding at period end	$ 40,000,000.0	$ 0
Money Pool
Short-term Debt [Line Items]
Borrowing limit	100,000,000	100,000,000
Amount outstanding at period end	100,000,000	0
Average amount outstanding	28,000,000	8,000,000
Maximum amount outstanding	$ 100,000,000	$ 100,000,000
Weighted average interest rate, computed on a daily basis	1.21%	2.42%
Weighted average interest rate at period end	1.15%