CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (USD $) In Thousands, unless otherwise specified	Total	COMMON STOCK (Note 7)	TREASURY STOCK (Note 7)	RETAINED EARNINGS	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	NONCONTROLLING INTERESTS	COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS
Balance at Dec. 31, 2009		$ 2,153,295	$ (3,812)	$ 1,298,213	$ (131,587)	$ 111,895
Increase (Decrease) in Shareholders' Equity
Issuance of common stock		268,077
Purchase of treasury stock			(82)
Reissuance of treasury stock used for stock compensation			1,655
Net income attributable to common shareholders	350,053			350,053			350,053
Common stock dividends				(224,305)
Net income attributable to noncontrolling interests	(20,156)					20,156
Net capital activities by noncontrolling interests						(40,152)
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS
Other comprehensive income (loss) attributable to common shareholders	(28,180)				(28,180)		(28,180)
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	321,873						321,873
Balance at Dec. 31, 2010	3,775,226	2,421,372	(2,239)	1,423,961	(159,767)	91,899
Increase (Decrease) in Shareholders' Equity
Issuance of common stock		22,875
Purchase of treasury stock			(3,720)
Reissuance of treasury stock used for stock compensation			1,242
Net income attributable to common shareholders	339,473			339,473			339,473
Common stock dividends				(228,951)
Net income attributable to noncontrolling interests	(27,467)					27,467
Net capital activities by noncontrolling interests						(10,630)
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS
Other comprehensive income (loss) attributable to common shareholders	7,605				7,604		7,605
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	347,078						347,078
Balance at Dec. 31, 2011	3,930,586	2,444,247	(4,717)	1,534,483	(152,163)	108,736
Increase (Decrease) in Shareholders' Equity
Issuance of common stock		22,676
Purchase of treasury stock			(4,607)
Reissuance of treasury stock used for stock compensation			5,113
Net income attributable to common shareholders	381,542			381,542			381,542
Common stock dividends				(291,923)
Net income attributable to noncontrolling interests	(31,622)					31,622
Net capital activities by noncontrolling interests						(10,875)
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS
Other comprehensive income (loss) attributable to common shareholders	38,155				38,155		38,155
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	419,697						419,697
Balance at Dec. 31, 2012	$ 4,102,289	$ 2,466,923	$ (4,211)	$ 1,624,102	$ (114,008)	$ 129,483