Condensed Financial Information of Registrant - Statements of Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Lease revenue									$ 975.2	$ 917.0	$ 900.1
Other revenue									70.7	60.7	61.3
Total Revenues	356.6	353.2	338.9	272.3	331.7	331.9	323.1	256.5	1,321.0	1,243.2	1,191.4
Maintenance expense									294.0	269.7	277.6
Depreciation									255.0	237.4	226.5
Operating lease expense									129.4	130.2	132.0
Other operating expense									26.1	24.2	27.8
Selling, general and administrative									178.3	160.2	155.3
Total Expenses									1,072.6	1,004.1	984.8
Net gain on asset dispositions									85.6	79.5	65.8
Interest expense, net									(166.6)	(166.6)	(168.9)
Other (expense) income									(8.4)	(8.2)	4.1
Income before Income Taxes and Share of Affiliates’ Earnings									159.0	143.8	107.6
Income tax benefit									(65.5)	(26.1)	(29.2)
Share of affiliates' earnings (net of tax)									75.8	19.6	32.4
Net Income	53.3	53.8	35.1	27.1	29.7	53.8	23.5	30.3	169.3	137.3	110.8
Foreign currency translation adjustments									25.8	25.0	(39.6)
Unrealized gain (loss) on securities									0.8	0.2	(0.2)
Unrealized gain (loss) on derivative instruments									22.4	11.7	(0.5)
Post-retirement benefit plans									52.9	(12.4)	(18.8)
Other comprehensive income (loss)									101.9	24.5	(59.1)
Comprehensive Income									271.2	161.8	51.7
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Lease revenue									543.0	504.5	477.7
Other revenue									51.3	43.5	44.4
Total Revenues									594.3	548.0	522.1
Maintenance expense									176.5	154.8	163.9
Depreciation									131.1	122.2	117.0
Operating lease expense									89.5	91.6	95.2
Other operating expense									12.7	12.0	11.5
Selling, general and administrative									131.1	118.4	113.3
Total Expenses									540.9	499.0	500.9
Net gain on asset dispositions									68.6	59.4	44.0
Interest expense, net									(63.7)	(65.4)	(72.8)
Other (expense) income									(7.0)	(4.4)	(2.4)
Income before Income Taxes and Share of Affiliates’ Earnings									51.3	38.6	(10.0)
Income tax benefit									(10.7)	1.0	4.8
Share of affiliates' earnings (net of tax)									128.7	97.7	116.0
Net Income									169.3	137.3	110.8
Foreign currency translation adjustments									25.8	25.0	(39.6)
Unrealized gain (loss) on securities									0.8	0.2	(0.2)
Unrealized gain (loss) on derivative instruments									22.4	11.7	(0.5)
Post-retirement benefit plans									52.9	(12.4)	(18.8)
Other comprehensive income (loss)									101.9	24.5	(59.1)
Comprehensive Income									$ 271.2	$ 161.8	$ 51.7