Changes in Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Increase (Decrease) in Equity
Balances			$ 2,495,855
Proceeds from the exercise of stock options, including related tax effect			11,503
Dividends declared			(53,221)
Conversion of 5.125% convertible senior notes			271,801
Equity based compensation and issuance of restricted stock			9,609
Contributions from noncontrolling investors			97
Distributions to noncontrolling investors			(653)
Net income (loss)	66,341	23,273	100,039	64,525
Balances	2,835,030		2,835,030
Common Stock [Member]
Increase (Decrease) in Equity
Balances			645
Proceeds from the exercise of stock options, including related tax effect			2
Balances	647		647
Additional Paid In Capital [Member]
Increase (Decrease) in Equity
Balances			1,085,694
Proceeds from the exercise of stock options, including related tax effect			11,501
Conversion of 5.125% convertible senior notes			(45,650)
Equity based compensation and issuance of restricted stock			7,376
Balances	1,058,921		1,058,921
Retained Earnings [Member]
Increase (Decrease) in Equity
Balances			2,179,513
Dividends declared			(53,221)
Equity based compensation and issuance of restricted stock			(27)
Net income (loss)			110,882
Balances	2,237,147		2,237,147
Treasury Stock [Member]
Increase (Decrease) in Equity
Balances			(718,529)
Conversion of 5.125% convertible senior notes			317,451
Equity based compensation and issuance of restricted stock			2,260
Balances	(398,818)		(398,818)
Noncontrolling Interest [Member]
Increase (Decrease) in Equity
Balances			(51,468)
Contributions from noncontrolling investors			97
Distributions to noncontrolling investors			(653)
Net income (loss)			(10,843)
Balances	(62,867)		(62,867)
Redeemable Noncontrolling Interest [Member]
Increase (Decrease) in Equity
Balances			116,514
Contributions from noncontrolling investors			7,666
Balances	$ 124,180		$ 124,180