Schedule I - Condensed Financial Information of Registrant - Statements of Comprehensive Income (Details) - 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
Condensed Financial Statements, Captions [Line Items]
Lease revenue									$ 1,130.1	$ 1,086.6	$ 975.2
Other revenue									84.8	78.1	70.7
Total Revenues	$ 378.7	$ 386.2	$ 365.3	$ 319.7	$ 401.4	$ 397.2	$ 365.8	$ 286.6	1,449.9	1,451.0	1,321.0
Maintenance expense									326.1	337.0	294.0
Depreciation									290.5	273.5	255.0
Operating lease expense									87.2	108.7	129.4
Other operating expense									38.4	28.9	26.1
Selling, general and administrative									192.4	189.2	178.3
Total Expenses									1,090.5	1,135.1	1,072.6
Net gain on asset dispositions									79.2	87.2	85.6
Interest expense, net									(155.1)	(158.4)	(166.6)
Other (expense) income									(13.2)	(13.5)	(8.4)
Income before Income Taxes and Share of Affiliates’ Earnings									270.3	231.2	159.0
Income tax benefit									(110.9)	(75.7)	(65.5)
Share of affiliates' earnings (net of tax)									45.9	49.5	75.8
Net Income	$ 58.2	$ 39.5	$ 45.4	$ 62.2	$ 58.5	$ 51.3	$ 53.1	$ 42.1	205.3	205.0	169.3
Foreign currency translation adjustments									(55.8)	(79.1)	25.8
Unrealized gain (loss) on securities									(0.6)	(0.1)	0.8
Unrealized gain (loss) on derivative instruments									(1.8)	3.0	22.4
Post-retirement benefit plans									7.8	(29.5)	52.9
Other comprehensive income (loss)									(50.4)	(105.7)	101.9
Comprehensive Income									154.9	99.3	271.2
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Lease revenue									718.3	669.7	543.0
Other revenue									66.7	60.2	51.3
Total Revenues									785.0	729.9	594.3
Maintenance expense									233.6	227.6	176.5
Depreciation									164.8	147.7	131.1
Operating lease expense									61.7	83.0	89.5
Other operating expense									25.4	17.1	12.7
Selling, general and administrative									149.2	139.7	131.1
Total Expenses									634.7	615.1	540.9
Net gain on asset dispositions									48.0	67.9	68.6
Interest expense, net									(68.7)	(66.7)	(63.7)
Other (expense) income									0.0	2.5	(7.0)
Income before Income Taxes and Share of Affiliates’ Earnings									129.6	118.5	51.3
Income tax benefit									(62.4)	(41.7)	(10.7)
Share of affiliates' earnings (net of tax)									138.1	128.2	128.7
Net Income									205.3	205.0	169.3
Foreign currency translation adjustments									(55.8)	(79.1)	25.8
Unrealized gain (loss) on securities									(0.6)	(0.1)	0.8
Unrealized gain (loss) on derivative instruments									(1.8)	3.0	22.4
Post-retirement benefit plans									7.8	(29.5)	52.9
Other comprehensive income (loss)									(50.4)	(105.7)	101.9
Comprehensive Income									$ 154.9	$ 99.3	$ 271.2