Investments (Net investment income on Leveraged and Direct Financing Leases) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Leveraged Leases, Income Statement, Income from Leveraged Leases	$ 12	$ 12	$ 24	$ 23
Leveraged Leases, Income Statement, Income Tax Expense on Leveraged Leases	(3)	(2)	(5)	(5)
Leveraged Leases, Income (Loss)	9	10	19	18
Capital Leases, Income Statement, Direct Financing Lease Revenue	27	27	47	47
Direct Financing Leases Income Statement Tax Expense on Direct Financing Leases	(6)	(6)	(10)	(10)
Direct Financing Leases Income Statement Net Income from Direct Financing Leases	$ 21	$ 21	$ 37	$ 37