Debt (Schedule of Letters of Credit Facilities) (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Letter of Credit [Member]
Debt Instrument [Line Items]
Letters of credit, Limit	$ 175,000,000.0
Letters of credit, Used	10,900,000
Letters of credit, Available	164,100,000
Letter of Credit [Member] | Bi-lateral Facility [Member]
Debt Instrument [Line Items]
Letters of credit, Limit	25,000,000.0
Letters of credit, Used	10,900,000
Letters of credit, Available	14,100,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Letters of credit, Limit	500,000,000.0	$ 500,000,000.0
Revolving Credit Facility [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Letters of credit, Limit	150,000,000.0	$ 150,000,000.0
Letters of credit, Available	$ 150,000,000.0