Summary Of Significant Accounting Policies (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Basis Of Presentation And Significant Accounting Policies [Line Items]
Income Tax Expense (Benefit)	$ 21
Excess Tax Benefit from Share-based Compensation, Operating Activities	2
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 32	$ 12