Income Taxes Reconciliation of Tax Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Gross tax contingencies - January 1	$ 407		$ 294	$ 229
Gross increases to tax positions in prior periods	351		78	91
Gross decreases to tax positions in prior periods	50		18	47
Gross increases to current period tax positions	20		54	26
Audit settlements paid	16		1	4
Lapse of statute of limitations	2		0	1
Gross tax contingencies - December 31	710	[1]	407	294
Tax contingencies, that if fully recognized, would decrease our effective tax rate	$ 604

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