Fair Value of Financial Instrument (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 1,659	$ 1,599
Fair Value	1,720	1,665
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Market Approach Valuation Technique [Member] | Senior Notes Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,580	1,500
Fair Value	1,643	1,567
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Income Approach Valuation Technique [Member] | Other Indebtedness [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	79	99
Fair Value	$ 77	$ 98