Investments (Operating Leases - Narrative) (Details) $ in Millions	Mar. 31, 2019 USD ($)
Investments, Debt and Equity Securities [Abstract]
Operating Leases, Future Minimum Payments Receivable, Current	$ 228
Operating Leases, Future Minimum Payments Receivable, in Two Years	243
Operating Leases, Future Minimum Payments Receivable, in Three Years	191
Operating Leases, Future Minimum Payments Receivable, in Four Years	162
Operating Leases, Future Minimum Payments Receivable, in Five Years	140
Operating Leases, Future Minimum Payments Receivable, Thereafter	974
Operating Leases, Future Minimum Payments Receivable	$ 1,900