Income Taxes Reconciliation of Tax Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Gross tax contingencies - January 1	$ 1,181		$ 710	$ 407
Gross increases to tax positions in prior periods	355		254	351
Gross decreases to tax positions in prior periods	133		22	50
Gross increases to current period tax positions	308		242	20
Audit settlements paid	0		0	16
Lapse of statute of limitations	1		3	2
Gross tax contingencies - December 31	1,710	[1]	$ 1,181	$ 710
Tax contingencies, that if fully recognized, would decrease our effective tax rate	$ 1,100

[1] Deferred tax assets related to net operating losses and tax credits are presented net of tax contingencies.