Changes in Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended						9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 5.125% convertible senior notes, due 2014	Dec. 31, 2011 5.125% convertible senior notes, due 2014	Sep. 30, 2012 Common Stock	Dec. 31, 2011 Common Stock	Sep. 30, 2012 Additional Paid-In Capital	Sep. 30, 2012 Retained Earnings	Sep. 30, 2012 Treasury Stock	Sep. 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			2,021						2,021
Dividends declared			(65,746)							(65,746)
Equity-based compensation and issuance of restricted stock			7,825						5,680	(24)	2,169
Conversion of 5.125% convertible senior notes			4						(1)		5
Contributions from noncontrolling investors			7,973									7,973
Distributions to noncontrolling investors			(110)									(110)
Net income (loss)	6,105	39,857	87,187	239,913						102,980		(15,793)
Balance at the end of the period	$ 2,339,054		$ 2,339,054				$ 636	$ 636	$ 1,033,857	$ 2,049,011	$ (720,479)	$ (23,971)
Note stated interest rate (as a percent)					5.125%	5.125%