Investments (Net investment income on Leveraged and Direct Financing Leases) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Leveraged Leases, Income Statement, Income from Leveraged Leases	$ 12	$ 12	$ 36	$ 35
Leveraged Leases, Income Statement, Income Tax Expense on Leveraged Leases	(3)	(2)	(8)	(7)
Leveraged Leases, Income (Loss)	9	10	28	28
Capital Leases, Income Statement, Direct Financing Lease Revenue	28	27	75	74
Direct Financing Leases Income Statement Tax Expense on Direct Financing Leases	(6)	(6)	(16)	(16)
Direct Financing Leases Income Statement Net Income from Direct Financing Leases	$ 22	$ 21	$ 59	$ 58