Venezuela (Details) $ / shares in Units, $ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) VEF / $	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) VEF / $ $ / shares	Dec. 31, 2014 USD ($) VEF / $ $ / shares
Foreign Currency [Line Items]
Pretax charge for Venezuela deconsolidation					$ 0	$ 1,084	$ 0
Reclassification due to Venezuela deconsolidation - cumulative translation adjustment, before-tax					0	(111)	0
Pretax remeasurement charges					$ 0	34	327
CP Venezuela
Foreign Currency [Line Items]
Aftertax charge for Venezuela deconsolidation		$ 1,058				1,058
Pretax charge for Venezuela deconsolidation						$ 1,084
Aftertax charge for Venezuela deconsolidation (in dollars per share) | $ / shares						$ 1.16
Charge for Venezuela deconsolidation - portion related to investment in CP Venezuela						$ 952
Reclassification due to Venezuela deconsolidation - cumulative translation adjustment, before-tax						111
Income Tax Benefit, Principally Related to Changes in Venezuela Foreign Currency Regime	$ 210
Pretax remeasurement charges						34	327
Aftertax remeasurement charge			$ 12	$ 10		$ 22	$ 214
Impact of aftertax remeasurement charge, diluted (in dollars per share) | $ / shares						$ 0.02	$ 0.23
VENEZUELA
Foreign Currency [Line Items]
SICAD exchange rate | VEF / $		13.50				13.50	12.00
Official exchange rate | VEF / $		6.30				6.30