Investments (Narrative) (Details) $ in Billions	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Investment [Line Items]
Equity Securities, FV-NI and without Readily Determinable Fair Value	$ 2.2	$ 2.0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	5,000
Total number of security positions	31,000
Equity Method Investments	$ 1.5	$ 1.5