New Accounting Pronouncements New Accounting Pronouncements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of income	$ 7,828	$ 7,869	$ 7,994
Reclassification of income	(46)	7	(30)
Prepaid Taxes				$ 105
Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of income		41	6
Reclassification of income		$ 41	$ 6
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset	275
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset	$ 315