Net Income Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Basic EPS:
Net income applicable to common stock	$ 84,335	$ 79,915	$ 140,714	$ 102,576
Amount allocable to common shareholders	99.00%	99.20%	99.10%	99.20%
Rights to undistributed earnings	83,496	79,291	139,420	101,775
Weighted average shares outstanding- basic	360,226,487	353,278,423	358,616,324	353,032,030
Net income per common share - basic	$ 0.23	$ 0.22	$ 0.39	$ 0.29
Restricted common shares issued, not vested, excluded from basic net income per common share	3,700,000	2,800,000	3,400,000	2,800,000
Diluted EPS:
Rights to undistribued earnings	$ 83,496	$ 79,291	$ 139,420	$ 101,775
Weighted average shares outstanding- basic	360,226,487	353,278,423	358,616,324	353,032,030
Effect of dilutive securities, stock options	5,163,793	2,407,023	4,536,910	2,119,082
Weighted average shares outstanding - diluted	365,390,280	355,685,446	363,153,234	355,151,112
Net Income Per Common Share, Diluted	$ 0.23	$ 0.22	$ 0.38	$ 0.29
Stock Options [Member]
Diluted EPS:
Antidilutive securities excluded from calculation of diluted net income per common share	10,300,000	25,800,000	14,400,000	25,200,000