Components of Debt (Parenthetical) (Detail)			12 Months Ended
	Dec. 31, 2013 Debentures Eleven Point Two Five Percent Due February One Two Thousand Nineteen Scenario, Adjustment	Dec. 31, 2012 Debentures Eleven Point Two Five Percent Due February One Two Thousand Nineteen Scenario, Adjustment	Dec. 31, 2013 Senior Notes Four Point Nine Five Percent Due April One Two Thousand Fourteen	Dec. 31, 2013 Senior Notes Five Point Five Zero Percent Due May Fifteen Two Thousand Fifteen	Dec. 31, 2013 Senior Notes Eight Point Six Zero Percent Due August Fifteen Two Thousand Sixteen	Dec. 31, 2013 Senior Notes Six Point One Two Five Percent Due January Fifteen Two Thousand Seventeen	Dec. 31, 2013 Senior Notes Seven Point Two Five Percent Due May Fifteen Two Thousand Eighteen	Dec. 31, 2013 Senior Notes Eleven Point Two Five Percent Due February One Two Thousand Nineteen Scenario, Actual		Dec. 31, 2013 Senior Notes Eight Point Two Five Percent Due March Fifteen Two Thousand Nineteen	Dec. 31, 2013 Senior Notes Seven Point Six Two Five Percent Due June Fifteen Two Thousand Twenty	Dec. 31, 2013 Senior Notes Seven Point Eight Seven Five Percent Due March Fifteen Two Thousand Twenty One	Dec. 31, 2013 Debentures Eight Point Eight Seven Five Percent Due April Fifteen Two Thousand Twenty One	Dec. 31, 2013 Senior Notes Seven Point Zero Percent Due February Fifteen Two Thousand Twenty Two	Dec. 31, 2013 Senior Notes Six Point Five Zero Percent Due November Fifteen Two Thousand Twenty Three	Dec. 31, 2013 Debentures Six Point Six Two Five Percent Due April Fifteen Two Thousand Twenty Nine	Dec. 31, 2013 Debentures Eight Point Eight Two Zero Percent Due April Fifteen Two Thousand Thirty One
Debt Instrument [Line Items]
Interest rate	12.75%	12.50%	4.95%	5.50%	8.60%	6.125%	7.25%	11.25%	[1]	8.25%	7.625%	7.875%	8.875%	7.00%	6.50%	6.625%	8.82%
Maturity date			Apr. 01, 2014	May 15, 2015	Aug. 15, 2016	Jan. 15, 2017	May 15, 2018	Feb. 01, 2019		Mar. 15, 2019	Jun. 15, 2020	Mar. 15, 2021	Apr. 15, 2021	Feb. 15, 2022	Nov. 15, 2023	Apr. 15, 2029	Apr. 15, 2031

[1] As of December 31, 2013 and 2012, the interest rate on the 11.25% senior notes due February 1, 2019 was 12.75% and 12.50%, respectively, as a result of downgrades in the ratings of the notes by the rating agencies.