Net Income Per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net Income Per Common Share:
Net income (loss)	$ 870,278	$ 901,806
Less: Preferred stock dividends	17,992	3,938
Net income (loss) available to common shareholders, prior to adjustment for dilutive potential common shares, if necessary	852,286	897,868
Add: Interest on Convertible Senior Notes, if dilutive	10,450	6,000
Net income (loss) available to common shareholders, as adjusted	$ 862,736	$ 903,868
Weighted average shares of common stock outstanding-basic	947,249,901	971,727,701
Add: Effect of dilutive stock options and Convertible Senior Notes, if dilutive	47,565,000	38,861,000
Weighted average shares of common stock outstanding-diluted	994,815,169	1,010,588,609