Components of Debt (Parenthetical) (Detail)					12 Months Ended
	Sep. 20, 2012 Revised Interest Rate Stated Percentage	Aug. 02, 2012 Revised Interest Rate Stated Percentage	Jun. 14, 2012 Revised Interest Rate Stated Percentage	May 17, 2011 Revised Interest Rate Stated Percentage	Dec. 31, 2012 Senior Notes Five Point Six Two Five Percent Due January Fifteen Two Thousand Twelve	Dec. 31, 2012 Senior Notes Four Point Nine Five Percent Due April One Two Thousand Fourteen	Dec. 31, 2012 Senior Notes Five Point Five Zero Percent Due May Fifteen Two Thousand Fifteen	Dec. 31, 2012 Senior Notes Eight Point Six Zero Percent Due August Fifteen Two Thousand Sixteen	Dec. 31, 2012 Senior Notes Six Point One Two Five Percent Due January Fifteen Two Thousand Seventeen	Dec. 31, 2012 Senior Notes Seven Point Two Five Percent Due May Fifteen Two Thousand Eighteen	Dec. 31, 2012 Senior Notes Eleven Point Two Five Percent Due February One Two Thousand Nineteen		Dec. 31, 2012 Senior Notes Eight Point Two Five Percent Due March Fifteen Two Thousand Nineteen	Dec. 31, 2012 Senior Notes Seven Point Six Two Five Percent Due June Fifteen Two Thousand Twenty	Dec. 31, 2012 Debentures Eight Point Eight Seven Five Percent Due April Fifteen Two Thousand Twenty One	Dec. 31, 2012 Debentures Six Point Six Two Five Percent Due April Fifteen Two Thousand Twenty Nine	Dec. 31, 2012 Debentures Eight Point Eight Two Zero Percent Due April Fifteen Two Thousand Thirty One
Debt Instrument [Line Items]
Interest rate	12.50%	12.25%	12.00%	11.75%	5.625%	4.95%	5.50%	8.60%	6.125%	7.25%	11.25%	[1]	8.25%	7.625%	8.875%	6.625%	8.82%
Maturity date					Jan. 15, 2012	Apr. 01, 2014	May 15, 2015	Aug. 15, 2016	Jan. 15, 2017	May 15, 2018	Feb. 01, 2019	[1]	Mar. 15, 2019	Jun. 15, 2020	Apr. 15, 2021	Apr. 15, 2029	Apr. 15, 2031

[1] On May 17, 2011, June 14, 2012, August 2, 2012 and September 20, 2012, the interest rate on the 11.25% senior notes due February 1, 2019 was increased to 11.75%, 12.0%, 12.25% and 12.50%, respectively, as a result of downgrades in the ratings of the notes by the rating agencies.