Business Segments (Narrative) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Disclosure Business Segments Summary Of Companys Segment Results [Abstract]
Number of operating segments	3
Extinguishment Of Debt [Line Items]
Net gains (losses) on extinguishment of debt	$ (1)	$ 3	$ 60