Consolidated Statement of Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net income	$ 178.3	$ 178.7
Net unrealized holding gains (losses) on available-for-sale securities (net of $6.7 and $0.0 tax benefit for the three months ended March 31, 2012 and 2011, respectively)	(11.5)	1.0
Increase in fair value of cash flow hedges	147.8	88.5
Less: Reclassification for realized gains included in net income	(84.2)	(56.0)
Net unrealized gains on cash flow hedges	63.6	32.5
Net actuarial loss for the period	0	3.5
Amortization of actuarial loss and prior service cost	13.9	10.0
Postretirement plan and workers compensation obligations	13.9	13.5
Foreign currency translation adjustment	12.7	0
Other Comprehensive Income	78.7	47.0
Comprehensive Income	257.0	225.7
Less: Comprehensive income attributable to noncontrolling interests	5.6	2.2
Comprehensive income attributable to common stockholders	251.4	223.5
Accumulated Other Comprehensive Income (Loss) [Member]
Net income	0
Net unrealized holding gains (losses) on available-for-sale securities (net of $6.7 and $0.0 tax benefit for the three months ended March 31, 2012 and 2011, respectively)	(11.5)
Net unrealized gains on cash flow hedges	63.6
Postretirement plan and workers compensation obligations	(13.9)
Foreign currency translation adjustment	$ 12.7