Net Income Per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Income Per Common Share:
Net income (loss)	$ 354,856	$ 192,458	$ (184,007)	$ 2,700,949
Less: Preferred stock dividends	17,992	17,992	53,976	53,976
Net income (loss) available to common shareholders, prior to adjustment for dilutive potential common shares, if necessary	336,864	174,466	(237,983)	2,646,973
Add: Interest on Convertible Senior Notes, if dilutive	12,226	1,075		31,351
Net income (loss) available to common shareholders, as adjusted	$ 349,090	$ 175,541	$ (237,983)	$ 2,678,324
Weighted average shares of common stock outstanding-basic	947,565,432	947,303,205	947,513,514	947,321,691
Add: Effect of stock awards and Convertible Senior Notes, if dilutive	39,750,095	8,387,266		47,997,979
Weighted average shares of common stock outstanding-diluted	987,315,527	955,690,471	947,513,514	995,319,670
Net income (loss) per share available (related) to common share:
Basic	$ 0.36	$ 0.18	$ (0.25)	$ 2.79
Diluted	$ 0.35	$ 0.18	$ (0.25)	$ 2.69