CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
NET INCOME	$ 234,718	$ 252,863	$ 407,152	$ 382,493
Derivative instruments:
Net unrealized loss, net of tax benefit of $95 and $47 for three months ended September 30, 2013 and 2012 and of $162 and $14,817 for nine months ended September 30, 2013 and 2012	(145)	(72)	(247)	(22,696)
Reclassification of net realized loss, net of tax benefit of $9,348 and $19,543 for three months ended September 30, 2013 and 2012 and $15,471 and $34,361 for nine months ended September 30, 2013 and 2012	14,310	29,935	23,685	52,632
Pension and other postretirement benefits activity, net of tax (expense) of $(625) and $(640) for three months ended September 30, 2013 and 2012 and $(807) and $(1,797) for nine months ended September 30, 2013 and 2012	957	980	1,235	2,752
Total other comprehensive income	15,122	30,843	24,673	32,688
COMPREHENSIVE INCOME	249,840	283,706	431,825	415,181
Less: Comprehensive income attributable to noncontrolling interests	8,555	8,040	25,338	23,582
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 241,285	$ 275,666	$ 406,487	$ 391,599