Earnings Per Common Share (Details) (USD $) In Thousands, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Numerator [Abstract]
Net income	$ 168,988	$ 148,031	$ 293,086	$ 608,476
Preferred dividends	(6,461)	(6,461)	(19,383)	(19,383)
Net income available to common shareholders	$ 162,527	$ 141,570	$ 273,703	$ 589,093
Denominator [Abstract]
Weighted average common shares outstanding - basic	131,560,851	146,993,373	132,090,354	152,979,948
Nonvested restricted shares	750,289	814,218	952,898	1,036,353
Stock options	4,829,789	5,738,436	5,499,306	5,935,293
Weighted average common shares and common share equivalents outstanding diluted	137,140,929	153,546,027	138,542,558	159,951,594
Basic	$ 1.24	$ 0.96	$ 2.07	$ 3.85
Diluted	$ 1.19	$ 0.92	$ 1.98	$ 3.68
Stock Options [Member]
Notes To Earnings Per Common Share [Abstract]
Antidilutive securities excluded from computation of earnings per share, amount	698,912	654,933	385,444	500,826