Debt (Narrative) (Details) - USD ($)			9 Months Ended
	Apr. 14, 2020	Dec. 04, 2015	Sep. 30, 2020	Apr. 10, 2020	Apr. 02, 2020	Mar. 23, 2020	Mar. 22, 2020
MetLife
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity						$ 300,000,000	$ 150,000,000
Prudential
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity				$ 425,000,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,000,000,000	$ 850,000,000
Debt instrument term	3 years	5 years
Line of credit facility, increase limit	$ 250,000,000
Line of credit facility, higher borrowing capacity option	1,250,000,000
Revolving Credit Facility, Individual Borrowings | Minimum
Line of Credit Facility [Line Items]
Debt instrument term			30 days
Revolving Credit Facility, Individual Borrowings | Maximum
Line of Credit Facility [Line Items]
Debt instrument term			180 days
Senior Notes
Line of Credit Facility [Line Items]
Debt covenant, maximum consolidated leverage ratio			3.5
MetLife 2030 Series D Notes | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, face amount			$ 125,000,000		$ 125,000,000
Stated interest rate			2.50%		2.50%
Prudential 2030 Series D Notes | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 75,000,000		$ 75,000,000
Stated interest rate			2.50%	2.50%