Income Taxes Items Accounting for Differences between Income Taxes Computed at Federal Statutory Rate and Provision Recorded for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2015	[1]	Sep. 30, 2015	[1]	Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2014	[1]	Sep. 30, 2014	[1]	Jun. 30, 2014	[1]	Mar. 31, 2014	[1]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income taxes computed at the federal statutory rate																	$ 549	$ (39)	$ 177
Effect of:
Impact of foreign tax differential																	350	136	(41)
State taxes, net of federal benefits																	37	29	14
Tax credits																	(99)	(85)	(84)
Nondeductible compensation																	149	117	86
Domestic production activities deduction																	44	20	11
Other, net																	8	29	20
Provision for income taxes, net	$ 453		$ 161		$ 266		$ 71		$ 205		$ (205)		$ 94		$ 73		$ 950	$ 167	$ 161

[1] The sum of quarterly amounts, including per share amounts, may not equal amounts reported for year-to-date periods. This is due to the effects of rounding and changes in the number of weighted-average shares outstanding for each period.