Changes in Equity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Increase (Decrease) in Equity
Balances			$ 2,795,527
Exercise of stock options proceeds, including related tax effect			7,154
Dividends declared			(66,515)
Distributions to noncontrolling investors, net			(1,165)
Equity-based compensation			11,448
Comprehensive income (loss)			52,279
Net income (loss)	$ 25,325	$ 66,341	52,279	$ 100,039
Balances	2,798,728		2,798,728
Common Stock
Increase (Decrease) in Equity
Balances			635
Exercise of stock options proceeds, including related tax effect			1
Balances	636		636
Additional Paid-in Capital
Increase (Decrease) in Equity
Balances			1,083,435
Exercise of stock options proceeds, including related tax effect			7,153
Equity-based compensation			9,081
Balances	1,099,669		1,099,669
Retained Earnings
Increase (Decrease) in Equity
Balances			2,227,843
Dividends declared			(66,515)
Equity-based compensation			(40)
Comprehensive income (loss)			62,311
Net income (loss)			62,311
Balances	2,223,599		2,223,599
Treasury Stock
Increase (Decrease) in Equity
Balances			(398,898)
Equity-based compensation			2,407
Balances	(396,491)		(396,491)
Noncontrolling Interests
Increase (Decrease) in Equity
Balances			(117,488)
Distributions to noncontrolling investors, net			(1,165)
Comprehensive income (loss)			(10,032)
Net income (loss)			(10,032)
Balances	(128,685)		(128,685)
Redeemable Noncontrolling Interest
Increase (Decrease) in Equity
Balances			126,340
Distributions to noncontrolling investors, net			(368)
Balances	$ 125,972		$ 125,972