Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Total	$ 1,573	$ 1,486
Less: current portion	(3)	(32)
Total long-term debt	1,570	1,454
7.25% Senior Notes due 2020
Debt Instrument [Line Items]
Debt carrying amount	400	400
6.375% Senior Notes Due 2022
Debt Instrument [Line Items]
Debt carrying amount	400
1.00% Senior Convertible Debentures due 2027
Debt Instrument [Line Items]
Debt carrying amount		25	[1]
3.25% Cash Convertible Senior Notes due 2014
Debt Instrument [Line Items]
Debt face amount	460	460
Debt discount	(61)	(67)
Cash conversion option derivative at fair value	75	49
Debt carrying amount	474	442
Term Loan
Debt Instrument [Line Items]
Debt face amount	300	619
Debt discount	(1)
Debt carrying amount	$ 299	$ 619

[1] The remaining outstanding Debentures were redeemed at par during the first quarter of 2012. See additional information below under 1.00% Senior Convertible Debentures due 2027.