Fair Value Measurements (Details 3) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Equity securities
Debt Securities, Available-for-sale [Abstract]
Cost Basis	$ 339	$ 254
Unrealized Gains	15	40
Unrealized Losses	(16)	0
Fair Value	338	294
Debt securities
Debt Securities, Available-for-sale [Line Items]
Cost Basis	714	774
Unrealized Gains	2	11
Unrealized Losses	(28)	(17)
Fair Value	$ 688	$ 768

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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