Debt - Additional Information (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	12 Months Ended			1 Months Ended						0 Months Ended	1 Months Ended	12 Months Ended		0 Months Ended		1 Months Ended	12 Months Ended		0 Months Ended		1 Months Ended	3 Months Ended		1 Months Ended		3 Months Ended
	Nov. 30, 2006	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jul. 31, 2012 Interest rate swap contract	Jun. 30, 2012 Interest rate swap contract	Apr. 30, 2012 Interest rate swap contract	Nov. 30, 2011 Interest rate swap contract	Dec. 31, 2013 Interest rate swap contract	Dec. 31, 2010 Interest rate swap contract	Jan. 07, 2014 Convertible Senior Notes 2013	Nov. 30, 2006 Convertible Senior Notes 2013	Dec. 31, 2013 Convertible Senior Notes 2013	Nov. 13, 2006 Convertible Senior Notes 2013	Jan. 09, 2012 Convertible Senior Notes 2011	Nov. 13, 2006 Convertible Senior Notes 2011	Nov. 30, 2006 Convertible Senior Notes 2011 and 2013	Dec. 31, 2013 Convertible Senior Notes 2011 and 2013	Dec. 31, 2011 Convertible Senior Notes 2011 and 2013	Jan. 07, 2014 Purchased Options	Jan. 09, 2012 Purchased Options	Nov. 30, 2006 Purchased Options	Dec. 31, 2011 Purchased Options Group 1	Dec. 31, 2013 Purchased Options Group 2	Nov. 30, 2006 Sold Warrants	Nov. 13, 2006 Sold Warrants	Mar. 31, 2012 Exercised Warrants	Dec. 31, 2013 Warrant	Jun. 30, 2013 Long-term Debt
Debt Instrument, Fair Value Disclosure																													$ 5,500,000,000
Issuance date	Nov. 13, 2006
Senior Notes														1,725,000,000		1,725,000,000
Proceeds from issuance of senior unsecured obligations																	3,500,000,000
Cash payment to noteholders for outstanding principal of converted Notes											1,700,000,000				1,700,000,000
Shares issued to noteholders for the excess of the conversion value over the principal amount of converted Notes											35				30
Value of the conversion value over the principal amount of converted Notes											858,000,000				661,000,000
Observation period													20 days
Conversion rate for the 2013 Notes will be 62.1978 shares of our common stock per one thousand dollars of principal amount of 2013 Notes													62.6978
Conversion ratio, principal amount basis													1,000
Conversion premium													26.50%
Conversion price													$ 15.95
Semi-annual interest rate														1.75%		1.75%
Debt Instrument, frequency of periodic payment												semi-annually
Effective interest rate																		5.60%	5.60%
Incremental common shares attributable to call options and warrants																						215			215
Aggregate amount paid for purchased options		0	70,000,000	141,000,000																		669,000,000
Purchased options exercised																							107
Purchased options shares received																				35	30
Purchased options remaining																								107
Common stock at an exercise price																									$ 19.55	$ 19.31
Proceeds from issuance of warrants																									391,000,000
Shares issues for exercised warrants																											32
Warrants and Rights Outstanding																												108,000,000
Conversion premium based on the closing price																									53.20%
Closing price per share																										$ 12.61
Aggregate notional amount of interest rate swap contracts designated as cash flow hedges										900,000,000
Realized loss on replaced interest rate swap contracts					46,000,000		23,000,000	141,000,000
Accumulated realized losses in other comprehensive income related to previously-anticipated interest payments reclassified from other comprehensive income and recognized in the consolidated income statements						40,000,000
Unrealized gain on derivatives									$ 176,000,000