Net Income Per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Income Per Common Share:
Net income	$ 1,028,749	$ 192,458	$ 1,638,213	$ 870,278	$ 700,495	$ 224,758	$ (91,159)	$ 901,806	$ 3,729,698	$ 1,735,900	$ 344,461
Less: Preferred stock dividends	17,992	17,992	17,992	17,992	19,717	9,367	6,508	3,938	71,968	39,530	16,854
Net income (loss) available to common shareholders, prior to adjustment for dilutive potential common shares, if necessary	1,010,757	174,466	1,620,221	852,286	680,778	215,391	(97,667)	897,868	3,657,730	1,696,370	327,607
Add: Interest on Convertible Senior Notes, if dilutive									67,056	27,843
Net income available to common shareholders, as adjusted									$ 3,724,786	$ 1,724,213	$ 327,607
Weighted average shares of common stock outstanding-basic									947,337,915	972,902,459	874,212,039
Add: Effect of dilutive stock options and Convertible Senior Notes, if dilutive									48,219,111	32,852,598	306,899
Weighted average shares of common stock outstanding-diluted									995,557,026	1,005,755,057	874,518,938
Net income (loss) per share available (related) to common share:
Basic	$ 1.07	$ 0.18	$ 1.71	$ 0.90	$ 0.70	$ 0.22	$ (0.10)	$ 0.92	$ 3.86	$ 1.74	$ 0.37
Diluted	$ 1.03	$ 0.18	$ 1.64	$ 0.87	$ 0.68	$ 0.22	$ (0.10)	$ 0.89	$ 3.74	$ 1.71	$ 0.37