Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Actuarial loss arising during the period, income tax	$ 0	$ (48)	$ 46
Reclassification of losses to net benefit cost, income tax	9	6	10
Reclassification of prior service costs to net benefit cost, income tax	0	1	2
Net derivative instrument gains (losses) arising during the period, income tax	3	(2)	1
Reclassification of realized derivative losses to net income, income tax	$ 1	$ (2)	$ 1