Long-Term Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Mar. 31, 2013	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2014	Apr. 30, 2014 Senior Secured Notes Due 2019 [Member]	Mar. 31, 2014 Senior Secured Notes Due 2019 [Member]	Mar. 31, 2014 Senior Secured Notes Due 2024 [Member]	Apr. 30, 2014 Senior Secured Notes Due 2020 [Member]	Apr. 30, 2014 Senior Unsecured Notes Due 2014 [Member]	Mar. 31, 2013 Senior Secured Second Lien Notes Due 2017 [Member]
Debt Instrument [Line Items]
Debt instrument, principal amount				$ 3,500		$ 1,500	$ 2,000
Debt instrument, stated interest					8.50%	3.75%	5.00%	7.875%	5.75%	9.875%
Redemption of aggregate principal amount					1,500			1,250	500
Pretax loss on retirement of debt	17	226	17
Redemption of aggregate principal amount										$ 201