Consolidated Statement of Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income	$ 41.6	$ 281.5	$ 427.7	$ 752.4
Unrealized holding losses on available-for-sale securities	(5.1)	(4.4)	(19.2)	(4.2)
Less: Reclassification for realized gains included in net income	0	(0.1)	0	(0.1)
Net unrealized holding losses on available-for-sale securities	(5.1)	(4.5)	(19.2)	(4.3)
Increase (decrease) in fair value of cash flow hedges	111.5	(135.9)	302.0	79.7
Less: Reclassification for realized gains included in net income	(57.7)	(61.5)	(179.2)	(180.3)
Net unrealized gains (losses) on cash flow hedges	53.8	(197.4)	122.8	(100.6)
Net actuarial loss for the period	0	0	0	3.5
Amortization of actuarial loss and prior service cost	13.9	10.2	41.6	30.2
Postretirement plan and workers compensation obligations	13.9	10.2	41.6	33.7
Foreign currency translation adjustment	13.8	0	20.4	0
Other Comprehensive Income (loss)	76.4	(191.7)	165.6	(71.2)
Comprehensive Income	118.0	89.8	593.3	681.2
Less: Comprehensive (loss) income attributable to noncontrolling interests	(1.3)	7.4	7.4	17.0
Comprehensive income attributable to common stockholders	119.3	82.4	585.9	664.2
Accumulated Other Comprehensive Income (Loss) [Member]
Net unrealized holding losses on available-for-sale securities			(19.2)
Net unrealized gains (losses) on cash flow hedges			122.8
Postretirement plan and workers compensation obligations			41.6
Foreign currency translation adjustment			$ 20.4