Condensed Consolidating Statements of Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Net income	$ 281	$ 258	$ 313	$ 328	$ 309	$ 283	$ 284	$ 223	$ 1,180	$ 1,099	$ 1,116
Other comprehensive income (loss), net of tax:
Defined benefit retirement plans gain (loss), net of tax expense (benefit) of $41, $(4), and $(64)									110	(13)	(119)
Foreign currency translation adjustments, net of tax benefit of -									1
Other comprehensive income (loss)									111	(13)	(119)
Comprehensive income									1,291	1,086	997
Parent
Condensed Financial Statements, Captions [Line Items]
Net income									1,180	1,099	1,116
Other comprehensive income (loss), net of tax:
Defined benefit retirement plans gain (loss), net of tax expense (benefit) of $41, $(4), and $(64)									110
Foreign currency translation adjustments, net of tax benefit of -									1
Other comprehensive income (loss)									111
Comprehensive income									1,291	1,099	1,116
Issuer
Condensed Financial Statements, Captions [Line Items]
Net income									1,182	1,100	1,115
Other comprehensive income (loss), net of tax:
Defined benefit retirement plans gain (loss), net of tax expense (benefit) of $41, $(4), and $(64)									110	(13)	(119)
Other comprehensive income (loss)									110	(13)	(119)
Comprehensive income									1,292	1,087	996
Non-guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income									688	661	659
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of tax benefit of -									1
Other comprehensive income (loss)									1
Comprehensive income									689	661	659
Total Consolidating Adjustments
Condensed Financial Statements, Captions [Line Items]
Net income									(1,870)	(1,761)	(1,774)
Other comprehensive income (loss), net of tax:
Defined benefit retirement plans gain (loss), net of tax expense (benefit) of $41, $(4), and $(64)									(110)
Foreign currency translation adjustments, net of tax benefit of -									(1)
Other comprehensive income (loss)									(111)
Comprehensive income									$ (1,981)	$ (1,761)	$ (1,774)