CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Comprehensive Income (Loss) [Line Items]
Net income (loss)	$ 40.4	$ (10.0)	$ 110.9	$ (12.9)
Available-for-sale securities and derivative instruments:
Net appreciation during the period	82.9	6.3	173.1	41.9
Portion of other-than-temporary impairment losses transferred from other comprehensive income	3.7	0.8	11.0	6.2
Benefit (provision) for deferred income taxes	(34.8)	9.6	(43.5)	11.1
Total available-for-sale securities and derivative instruments	51.8	16.7	140.6	59.2
Amortization recognized as net periodic benefit costs:
Net actuarial loss	3.3	3.9	9.8	11.6
Prior service cost	(0.9)	(1.3)	(2.8)	(3.9)
Total amortization recognized as net periodic benefit costs	2.4	2.6	7.0	7.7
Provision for deferred income taxes	(0.8)	(0.9)	(2.4)	(2.7)
Total pension and postretirement benefits	1.6	1.7	4.6	5.0
Cumulative foreign currency translation adjustment:
Amount recognized as cumulative foreign currency translation during the period	11.6	(14.5)	13.0	(14.5)
Benefit (provision) for deferred income taxes	(4.1)	5.1	(4.6)	5.1
Total cumulative foreign currency translation adjustment	7.5	(9.4)	8.4	(9.4)
Other comprehensive income	60.9	9.0	153.6	54.8
Comprehensive income (loss)	$ 101.3	$ (1.0)	$ 264.5	$ 41.9