Investments Investments (Net Investment Income on Leveraged and Direct Financing Leases) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Leveraged Leases, Income Statement, Income from Leveraged Leases	$ 47	$ 19	$ 51
Leveraged Leases, Income Statement, Income Tax Expense on Leveraged Leases	10	7	18
Leveraged Leases, Income (Loss)	37	12	33
Capital Leases, Income Statement, Direct Financing Lease Revenue	95	89	51
Direct Financing Leases Income Statement Tax Expense on Direct Financing Leases	20	31	18
Direct Financing Leases Income Statement Net Income from Direct Financing Leases	$ 75	$ 58	$ 33