Earnings per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Amounts attributable to common stockholders:
Income from continuing operations	$ 76,533	$ 112,339	$ 315,494	$ 302,095
Income (loss) from discontinued operations	0	60,428	19,332	57,911
Net Income (Loss) Available to Common Stockholders, Basic	76,533	172,767	334,826	360,006
Preferred Stock Dividends, Income Statement Impact	(12)	(15)	38	44
Income attributable to common stockholders (numerator for basic EPS)	$ 76,521	$ 172,752	$ 334,788	$ 359,962
Denominator (in thousands):
Weighted average shares used in basic EPS	200,593	201,294	200,266	202,664
Effect of dilutive shares:
Incremental Common Shares Attributable to Conversion of Preferred Stock	2	2	2	2
Incremental Common Shares Attributable to Conversion of Preference Stock	399	447	399	451
Incremental Common Shares Attributable to Share-based Payment Arrangements	608	451	458	366
Weighted-average shares used in diluted EPS	201,602	202,194	201,125	203,483
Income from continuing operations	$ 0.38	$ 0.56	$ 1.58	$ 1.49
Income (loss) from discontinued operations	$ 0.00	$ 0.30	$ 0.10	$ 0.29
Net income	$ 0.38	$ 0.86	$ 1.67	$ 1.78
Diluted earnings per share:
Income from continuing operations	$ 0.38	$ 0.56	$ 1.57	$ 1.48
Income (loss) from discontinued operations	$ 0.00	$ 0.30	$ 0.10	$ 0.28
Net income	$ 0.38	$ 0.85	$ 1.66	$ 1.77
Anti-dilutive shares (in thousands):
Anti-dilutive shares not used in calculating diluted weighted-average shares	13,607	15,442	14,391	15,435