Fair Value Measurements (Financial Instruments At Fair Value, Excluding Derivative Financial Instruments) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Carrying Value [Member]
Financial assets:
Investments	$ 59		$ 93
Other	31		30
Total financial assets	90		123
Financial liabilities:
Long-term debt	3,006	[1]	3,008	[1]
Deferred credits and other liabilities	23		21
Total financial liabilities	3,029		3,029
Fair Value [Member]
Financial assets:
Investments	263		289
Other	33		31
Total financial assets	296		320
Financial liabilities:
Long-term debt	3,559	[1]	3,203	[1]
Deferred credits and other liabilities	23		21
Total financial liabilities	$ 3,582		$ 3,224

[1] Excludes capital leases.