Statements of Condensed Consolidated Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income	Noncontrolling Interests in Consolidated Subsidiaries
Balance at Dec. 31, 2011	$ 3,593,830	$ 1,261,779	$ 2,143,910	$ 188,141
Balance (in shares) at Dec. 31, 2011		149,477
Increase (Decrease) in Stockholders' Equity
Net income	103,481		103,481
Other comprehensive loss	(7,446)			(7,446)
Dividends on common stock ($0.06 and $0.44 per share for periods ending June 30, 2013 and 2012, respectively)	(65,887)		(65,887)
Stock-based compensation plans, net	22,030	22,030
Stock-based compensation plans, net (in shares)		118
Balance at Jun. 30, 2012	3,646,008	1,283,809	2,181,504	180,695
Balance (in shares) at Jun. 30, 2012		149,595
Balance at Dec. 31, 2012	3,888,802	1,308,771	2,195,502	99,547	284,982
Balance (in shares) at Dec. 31, 2012		150,109
Increase (Decrease) in Stockholders' Equity
Net income	203,399		187,111		16,288
Other comprehensive loss	(14,554)			(14,554)
Dividends on common stock ($0.06 and $0.44 per share for periods ending June 30, 2013 and 2012, respectively)	(9,038)		(9,038)
Stock-based compensation plans, net	43,966	43,737			229
Stock-based compensation plans, net (in shares)		485
Distributions to noncontrolling interests ($0.72 per common unit)	(10,350)				(10,350)
Balance at Jun. 30, 2013	$ 4,102,225	$ 1,352,508	$ 2,373,575	$ 84,993	$ 291,149
Balance (in shares) at Jun. 30, 2013		150,594