Changes in Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended						6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 5.125% convertible senior notes, due 2014	Dec. 31, 2011 5.125% convertible senior notes, due 2014	Jun. 30, 2012 Common Stock	Dec. 31, 2011 Common Stock	Jun. 30, 2012 Additional Paid-In Capital	Jun. 30, 2012 Retained Earnings	Jun. 30, 2012 Treasury Stock	Jun. 30, 2012 Noncontrolling Interests
Increase (Decrease) in Equity
Balance at the beginning of the period			$ 2,299,900				$ 636	$ 636	$ 1,026,157	$ 2,011,801	$ (722,653)	$ (16,041)
Proceeds from the exercise of stock options, including related tax effect			1,438						1,438
Dividends declared			(43,840)							(43,840)
Equity-based compensation and issuance of restricted stock			7,661						5,491		2,170
Conversion of 5.125% convertible senior notes			2								2
Contributions from noncontrolling investors			7,973									7,973
Distributions to noncontrolling investor			(80)									(80)
Net income (loss)	39,305	95,826	81,082	200,056						90,147		(9,065)
Balance at the end of the period	$ 2,354,136		$ 2,354,136				$ 636	$ 636	$ 1,033,086	$ 2,058,108	$ (720,481)	$ (17,213)
Long-term debt
Note stated interest rate (as a percent)					5.125%	5.125%