Accumulated Other Comprehensive Loss (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Currency translation adjustments, Beginning Balance	$ (16.5)	$ (16.5)	$ (17.1)
Currency translation adjustments, Other comprehensive income (loss), net of tax, before reclassifications	(2.0)	0	0
Currency translation adjustments, Amounts reclassified from accumulated other comprehensive loss, net of tax	0	0	0.6
Currency translation adjustments, Amounts reclassified from accumulated other comprehensive loss, tax benefit	0	0	0.4
Currency translation adjustments, Less: noncontrolling interest	0	0	0
Currency translation adjustments, Other comprehensive income (loss)	(2.0)	0	0.6
Currency translation adjustments, Ending Balance	(18.5)	(16.5)	(16.5)
Unrealized loss on derivative financial instruments, Beginning Balance	(18.7)	(34.8)	(46.2)
Unrealized loss on derivative financial instruments, Other comprehensive income (loss), net of tax, before reclassifications	(1.2)	0.8	7.2
Unrealized loss on derivative financial instruments, Amounts reclassified from accumulated other comprehensive loss, net of tax	16.0	18.1	5.8
Unrealized loss on derivative financial instruments, Amounts reclassified from accumulated other comprehensive loss, tax benefit	8.4	8.7	3.2
Unrealized loss on derivative financial instruments, Less: noncontrolling interest	(3.0)	(4.2)	(1.6)
Unrealized loss on derivative financial instruments, Other comprehensive income (loss)	11.8	14.7	11.4
Unrealized loss on derivative financial instruments, Sale of interests in partially-owned leasing subsidiaries	0.3	13.2
Unrealized loss on derivative financial instruments, Repurchase of interests in partially-owned leasing subsidiary		(11.8)
Unrealized loss on derivative financial instruments, Ending Balance	(6.6)	(18.7)	(34.8)
Net actuarial gains/(losses) of defined benefit plans, Beginning Balance	(43.0)	(98.8)	(70.7)
Net actuarial gains/(losses) of defined benefit plans, Other comprehensive income (loss), net of tax, before reclassifications	(45.1)	52.7	(30.3)
Net actuarial gains/(losses) of defined benefit plans, Amounts reclassified from accumulated other comprehensive loss, net of tax	1.3	3.1	2.2
Net actuarial gains/(losses) of defined benefit plans, Amounts reclassified from accumulated other comprehensive loss, tax benefit	0.8	1.9	1.1
Net actuarial gains/(losses) of defined benefit plans, Less: noncontrolling interest	0	0	0
Net actuarial gains/(losses) of defined benefit plans, Other comprehensive income (loss)	(43.8)	55.8	(28.1)
Net actuarial gains/(losses) of defined benefit plans, Ending Balance	(86.8)	(43.0)	(98.8)
Accumulated Other Comprehensive Loss, Beginning Balance	(78.2)	(150.1)	(134.0)
Accumulated Other Comprehensive Loss, Other comprehensive income (loss), net of tax, before reclassifications	(48.3)	53.5	(23.1)
Accumulated Other Comprehensive Loss, Amounts reclassified from accumulated other comprehensive loss, net of tax	17.3	21.2	8.6
Accumulated Other Comprehensive Loss, Amounts reclassified from accumulated other comprehensive loss, tax benefit	9.2	10.6	4.7
Accumulated Other Comprehensive Loss, Less: noncontrolling interest	(3.0)	(4.2)	(1.6)
Accumulated Other Comprehensive Loss, Other comprehensive income (loss)	(34.0)	70.5	(16.1)
Accumulated Other Comprehensive Loss, Ending Balance	(111.9)	(78.2)	(150.1)
Statement [Line Items]
Before-tax reclassification of net actuarial gains/(losses) of defined benefit plans included in cost of revenues	(2.1)	(4.9)	(3.2)
Cost of revenues
Statement [Line Items]
Before-tax reclassification of net actuarial gains/(losses) of defined benefit plans included in cost of revenues	$ 1.7	$ 4.0	$ 2.7