CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
NET INCOME	$ 439,966	$ 413,164	$ 366,940
Derivative instruments:
Net unrealized loss, net of tax benefit of $140, $14,900, and $37,389 (Note 17)	(213)	(22,763)	(57,271)
Reclassification of net realized loss, net of tax benefit of $17,472, $39,120, and $46,288 (Note 17)	26,747	59,887	70,902
Pension and other postretirement benefits activity, net of tax (expense) benefit of $(6,156), $(651), and $3,935 (Note 8)	9,421	1,031	(6,026)
Total other comprehensive income	35,955	38,155	7,605
COMPREHENSIVE INCOME	475,921	451,319	374,545
Less: Comprehensive income attributable to noncontrolling interests	33,892	31,622	27,467
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 442,029	$ 419,697	$ 347,078