Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net loss	$ (470.2)	$ (301.9)	$ (1,043.5)	$ (173.3)	$ (513.0)	$ (149.0)	$ (71.2)	$ (44.1)	$ (1,988.9)	$ (777.3)	$ (512.6)
Net change in unrealized (losses) gains on available-for-sale securities (net of respective tax (benefit) provision of ($0.1), ($0.5) and $0.5)
Unrealized holding losses on available-for-sale securities									0.0	(3.7)	(12.3)
Reclassification for realized losses included in net loss									0.0	2.9	12.8
Net change in unrealized (losses) gains on available-for-sale securities									0.0	(0.8)	0.5
Net unrealized gains (losses) on cash flow hedges (net of respective tax provision (benefit) of $72.2, ($54.6) and ($300.0))
Decrease in fair value of cash flow hedges									(131.3)	(195.0)	(333.6)
Reclassification for realized losses (gains) included in net loss									251.7	(10.2)	(209.6)
Net unrealized gains (losses) on cash flow hedges									120.4	(205.2)	(543.2)
Postretirement plans and workers' compensation obligations (net of respective tax provision (benefit) of $36.2, $(10.3) and $121.7)
Prior service credit (cost) for the period									10.4	11.4	(1.4)
Net actuarial gain (loss) for the period									18.1	(142.7)	110.9
Amortization of actuarial loss and prior service cost included in net loss									31.9	32.7	95.7
Postretirement plans and workers' compensation obligations									60.4	(98.6)	205.2
Foreign currency translation adjustment									(34.9)	(41.0)	(92.7)
Other comprehensive income (loss), net of income taxes									145.9	(345.6)	(430.2)
Comprehensive loss									(1,843.0)	(1,122.9)	(942.8)
Less: Comprehensive income attributable to noncontrolling interests									7.1	9.7	12.3
Comprehensive loss attributable to common stockholders									$ (1,850.1)	$ (1,132.6)	$ (955.1)