COMMON SHAREHOLDER EQUIT AND NCI (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Shareholders' Equity, Beginning Balance				$ 9,976,815					$ 9,976,815
Net Income	$ 183,700	$ 237,800	$ 209,400	255,100	$ 223,600	$ 236,500	$ 129,200	$ 237,800	886,004	$ 827,065	$ 793,689
Net Income Attributable to Noncontrolling Interests									7,519	7,519	7,682
Other Comprehensive Income (Loss), Net of Tax									7,165	(27,978)	26,823
Shareholders' Equity, Ending Balance	10,352,215				9,976,815				10,352,215	9,976,815
Common Shareholders Equity [Member]
Shareholders' Equity, Beginning Balance											9,237,100
Net Income									886,004	827,065
Dividends on Common Shares									(529,791)	(496,524)	(462,741)
Dividends on Preferred Stock									(7,519)	(7,519)	(7,682)
Issuance of Common Shares									9,468	6,609	11,078
Other Transcations, Net									0	63,600	13,200
Other Comprehensive Income (Loss), Net of Tax									7,165	(27,978)	26,823
Preferred Stock Member
Shareholders' Equity, Beginning Balance				$ 155,600				$ 155,600	155,600	155,600	155,600
Dividends on Preferred Stock									0	(7,500)	(7,700)
Net Income Attributable to Noncontrolling Interests									0	7,500	7,700
Shareholders' Equity, Ending Balance	$ 155,600				$ 155,600				$ 155,600	$ 155,600	$ 155,600