Changes in Equity (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Increase (Decrease) in Equity
Balance at the beginning of the period			$ 2,076,835
Proceeds from the exercise of stock options, including related tax effect			12,865
Dividends declared			(43,695)
Equity-based compensation and issuance of restricted stock			9,246
Contributions from noncontrolling investors			2,393
Distributions to noncontrolling investor			(506)
Net income	95,826	46,797	200,056	110,186
Comprehensive income (loss)			200,056
Balance at the end of the period	2,257,194		2,257,194
Common Stock
Increase (Decrease) in Equity
Balance at the beginning of the period			633
Proceeds from the exercise of stock options, including related tax effect			3
Balance at the end of the period	636		636
Additional Paid-In Capital
Increase (Decrease) in Equity
Balance at the beginning of the period			998,728
Proceeds from the exercise of stock options, including related tax effect			12,862
Equity-based compensation and issuance of restricted stock			7,471
Balance at the end of the period	1,019,061		1,019,061
Retained Earnings
Increase (Decrease) in Equity
Balance at the beginning of the period			1,821,133
Dividends declared			(43,695)
Net income			204,613
Comprehensive income (loss)			204,613
Balance at the end of the period	1,982,051		1,982,051
Treasury Stock
Increase (Decrease) in Equity
Balance at the beginning of the period			(727,624)
Equity-based compensation and issuance of restricted stock			1,775
Balance at the end of the period	(725,849)		(725,849)
Noncontrolling Interests
Increase (Decrease) in Equity
Balance at the beginning of the period			(16,035)
Contributions from noncontrolling investors			2,393
Distributions to noncontrolling investor			(506)
Net income			(4,557)
Comprehensive income (loss)			(4,557)
Balance at the end of the period	$ (18,705)		$ (18,705)