Employee Benefit Plans, Pre-Tax Amounts Recognized in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net (gain) loss reclassified into income:
Total changes in other comprehensive income (loss)	$ 49	$ (65)	$ (98)
Pension Plans [Member]
Net gain (loss) arising during the year:
Net actuarial gain (loss)	(8)	(73)	(145)
Prior service (cost) credit	7	(4)	0
Net (gain) loss reclassified into income:
Net actuarial (gain) loss	65	53	49
Prior service credit	(18)	(20)	(20)
Curtailment and settlement loss	7	4	0
Total changes in other comprehensive income (loss)	53	(40)	(116)
Other Postretirement Benefit Plans [Member]
Net gain (loss) arising during the year:
Net actuarial gain (loss)	9	(6)	35
Prior service (cost) credit	0	0	0
Net (gain) loss reclassified into income:
Net actuarial (gain) loss	(2)	(3)	(1)
Prior service credit	(11)	(16)	(16)
Curtailment and settlement loss	0	0	0
Total changes in other comprehensive income (loss)	$ (4)	$ (25)	$ 18