Long-Term Debt - Outstanding Long-Term Debt (Parenthetical) (Detail)	9 Months Ended										9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 9.57% bond, due May 1, 2018 [Member]	Sep. 30, 2013 10.03% bond, due May 1, 2018 [Member]	Sep. 30, 2013 9.08% bond, due June 1, 2022 [Member]	Sep. 30, 2013 7.83% note, due January 1, 2015 [Member]	Sep. 30, 2013 6.64% note, due October 31, 2017 [Member]	Sep. 30, 2013 5.50% note, due October 12, 2020 [Member]	Sep. 30, 2013 5.93% note, due October 31, 2023 [Member]	Sep. 30, 2013 5.68% note, due June 30, 2026 [Member]	Jun. 30, 2011 5.68% note, due June 30, 2026 [Member]	Sep. 30, 2013 8.25% due March 1, 2014 [Member]	Sep. 30, 2013 6.43% note, due May 2, 2028 [Member]	May 02, 2013 6.43% note, due May 2, 2028 [Member]
Debt Instrument [Line Items]
Long-term debt, interest percentage		9.57%	10.03%	9.08%	7.80%	6.64%	5.50%	5.93%	5.68%	5.68%	8.25%	6.43%	6.40%
Debt instrument, maturity date	May 02, 2028	May 01, 2018	May 01, 2018	Jun. 01, 2022	Jan. 01, 2015	Oct. 31, 2017	Oct. 12, 2020	Oct. 31, 2023	Jun. 30, 2026		Mar. 01, 2014