Schedule of Reconciling Items to Loss from Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Items not allocated to segments:
Postretirement benefit expense	$ (74)	[1]	$ (96)	[1]	$ (228)	[1]	$ (287)	[1]
Other items not allocated to segments:
Labor agreement lump sum payments (Note 16)	(35)				(35)
Net loss on the sale of assets (Note 4)					(310)
Property tax settlements					19	[2]
Total other items not allocated to segments	(35)				(326)
Income (loss) from operations	62		199		242		408
Unallocated Amount to Segment
Other items not allocated to segments:
Income (loss) from operations	$ (109)		$ (96)		$ (554)		$ (287)

[1] Consists of the net periodic benefit cost elements, other than service cost and amortization of prior service cost for active employees, associated with our pension, retiree health care and life insurance benefit plans.

[2] Reflects the effects of Michigan property tax settlements that occurred in the first quarter 2012.