Accumulated Other Comprehensive Income (Loss) Reclassifications in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income, net	$ 52	$ 15	$ 54
Provision for (benefit from) income taxes, investments	(300)	258	(138)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	11	(2)	51
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	11	(2)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of pension and other post-retirement items	0	(2)	(2)
Settlement gain	14	0	0
Provision for (benefit from) income taxes	(3)	0	1
Amounts reclassified from accumulated other comprehensive income (loss)	11	(2)	(1)
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income, net	0	0	54
Provision for (benefit from) income taxes, investments	0	0	(2)
Income (Loss) from Continuing Operations, including portion attributable to noncontrolling interest	$ 0	$ 0	$ 52