New And Significant Accounting Policies (Reclassifications out of Accumulated Other Comprehensive Income) (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Disclosure New And Significant Accounting Policies Reclassifications Out Of Accumulated Other Comprehensive Income [Abstract]
Beginning accumulated other comprehensive income, tax	$ 101
Other Comprehensive Income Before Reclassifications, tax	9
Amortization of prior service cost income tax	5
Amortization of actuarial gains (losses) income tax	11
Ending accumulated other comprehensive income, tax	$ 94