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
Changes in equity
Balance	$ 4,377,701	$ 4,152,330	$ 4,340,460	$ 4,102,289
Net income	141,384	139,598	166,075	172,434
Other comprehensive income	685	3,474	3,836	9,551
COMPREHENSIVE INCOME	142,069	143,072	169,911	181,985
Issuance of capital stock	2,280	2,363	4,872	4,937
Reissuance (purchase) of treasury stock - net	654	366	4,119	(5,905)
Other (primarily stock compensation)	292	185	3,634	15,010
Dividends on common stock	(125,265)	(119,885)	(125,265)	(119,885)
Net capital activities by noncontrolling interests	(15,869)	(9,196)	(15,869)	(9,196)
Balance	4,381,862	4,169,235	4,381,862	4,169,235
Common Shareholders
Changes in equity
Balance	4,222,786	4,014,455	4,194,470	3,972,806
Net income	132,458	131,207	148,224	155,651
Other comprehensive income	685	3,474	3,836	9,551
COMPREHENSIVE INCOME	133,143	134,681	152,060	165,202
Issuance of capital stock	2,280	2,363	4,872	4,937
Reissuance (purchase) of treasury stock - net	654	366	4,119	(5,905)
Other (primarily stock compensation)	292	185	3,634	15,010
Dividends on common stock	(125,265)	(119,885)	(125,265)	(119,885)
Balance	4,233,890	4,032,165	4,233,890	4,032,165
Noncontrolling Interests
Changes in equity
Balance	154,915	137,875	145,990	129,483
Net income	8,926	8,391	17,851	16,783
COMPREHENSIVE INCOME	8,926	8,391	17,851	16,783
Net capital activities by noncontrolling interests	(15,869)	(9,196)	(15,869)	(9,196)
Balance	$ 147,972	$ 137,070	$ 147,972	$ 137,070