Financial Statements for Guarantors of the Senior Notes (Details 3) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net income	$ 74.2	$ 89.6	$ 98.8	$ 102.1	$ 204.0	$ 212.2	$ 220.8	$ 189.0	$ 364.7	$ 826.0	$ 709.3
Equity in earnings of subsidiaries, net of taxes									0.0	0.0	0.0
Other									725.5	113.7	108.9
Net cash provided by operating activities - continuing operations									1,090.2	939.7	818.2
Net cash provided by operating activities - discontinued									0.0	0.0	1.0
Net cash provided (required) by operating activities									1,090.2	939.7	819.2
Investing activities:
(Increase) decrease in short-term marketable securities									(149.8)	(9.9)	74.7
Proceeds from railcar lease fleet sales owned more than one year									37.7	514.6	265.8
Proceeds from disposition of property and other assets									16.0	8.2	23.0
Capital expenditures – leasing									(799.1)	(833.8)	(245.3)
Capital expenditures – manufacturing and other									(134.3)	(196.0)	(219.3)
Acquisitions, net of cash acquired									0.0	(46.2)	(714.4)
(Increase) decrease in investment in partially-owned subsidiaries									0.0	0.0	0.0
Divestitures									0.0	51.3	0.0
Other									6.8	0.5	0.8
Net cash required by investing activities - continuing operations									(1,022.7)	(511.3)	(814.7)
Net cash provided by investing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by investing activities									(1,022.7)	(511.3)	(814.7)
Financing activities:
Proceeds from issuance of common stock, net									0.0	0.3	0.6
Excess tax benefits from stock-based compensation									1.0	13.3	24.4
Payments to retire debt									(162.5)	(587.2)	(186.6)
Proceeds from issuance of debt									0.0	242.4	727.3
(Increase) decrease in restricted cash									17.6	48.3	1.0
Shares repurchased									(34.7)	(115.0)	(36.5)
Dividends paid to common shareholders									(66.7)	(64.9)	(54.4)
Purchase of shares to satisfy employee tax on vested stock									(16.3)	(27.5)	(38.3)
Contributions from noncontrolling interest									0.0	0.0	49.6
Contributions from controlling interest in partially-owned leasing subsidiaries									0.0	0.0	0.0
Distributions to noncontrolling interest									(26.4)	(39.2)	(28.2)
Distributions to controlling interest in partially-owned leasing subsidiaries									0.0	0.0	0.0
Change in intercompany financing between entities									0.0	0.0	0.0
Other									(2.1)	(0.8)	(2.5)
Net cash provided (required) by financing activities - continuing									(290.1)	(530.3)	456.4
Net cash provided (required) by financing activities - discontinued									0.0	0.0	(1.5)
Net cash provided (required) by financing activities									(290.1)	(530.3)	454.9
Net increase (decrease) in cash and cash equivalents									(222.6)	(101.9)	459.4
Cash and cash equivalents at beginning of period				786.0	786.0			887.9	786.0	887.9	428.5
Cash and cash equivalents at end of period	563.4				786.0	786.0			563.4	786.0	887.9
Reportable legal entities | Parent
Operating activities:
Net income									343.6	796.5	678.2
Equity in earnings of subsidiaries, net of taxes									(387.5)	(920.0)	(741.7)
Other									64.5	57.8	(26.5)
Net cash provided by operating activities - continuing operations									20.6	(65.7)	(90.0)
Net cash provided by operating activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by operating activities									20.6	(65.7)	(90.0)
Investing activities:
(Increase) decrease in short-term marketable securities									(149.8)	(9.9)	74.7
Proceeds from railcar lease fleet sales owned more than one year									0.0	0.0	0.0
Proceeds from disposition of property and other assets									0.0	0.0	0.3
Capital expenditures – leasing									0.0	0.0	0.0
Capital expenditures – manufacturing and other									(18.0)	(14.5)	(8.3)
Acquisitions, net of cash acquired									0.0	0.0	0.0
(Increase) decrease in investment in partially-owned subsidiaries									0.0	0.0	0.0
Divestitures									0.0	0.0	0.0
Other									0.0	0.0	0.9
Net cash required by investing activities - continuing operations									(167.8)	(24.4)	67.6
Net cash provided by investing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by investing activities									(167.8)	(24.4)	67.6
Financing activities:
Proceeds from issuance of common stock, net									0.0	0.3	0.6
Excess tax benefits from stock-based compensation									1.0	13.3	24.4
Payments to retire debt									0.0	0.0	(0.5)
Proceeds from issuance of debt									0.0	(1.5)	395.7
(Increase) decrease in restricted cash									0.0	0.0	0.0
Shares repurchased									(34.7)	(115.0)	(36.5)
Dividends paid to common shareholders									(66.7)	(64.9)	(54.4)
Purchase of shares to satisfy employee tax on vested stock									(16.3)	(27.5)	(38.3)
Contributions from noncontrolling interest									0.0	0.0	0.0
Contributions from controlling interest in partially-owned leasing subsidiaries									0.0	0.0	0.0
Distributions to noncontrolling interest									0.0	0.0	0.0
Distributions to controlling interest in partially-owned leasing subsidiaries									0.0	0.0	0.0
Change in intercompany financing between entities									33.5	226.0	149.4
Other									0.0	0.0	0.0
Net cash provided (required) by financing activities - continuing									(83.2)	30.7	440.4
Net cash provided (required) by financing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by financing activities									(83.2)	30.7	440.4
Net increase (decrease) in cash and cash equivalents									(230.4)	(59.4)	418.0
Cash and cash equivalents at beginning of period				768.3	768.3			827.7	768.3	827.7	409.7
Cash and cash equivalents at end of period	537.9				768.3	768.3			537.9	768.3	827.7
Reportable legal entities | Combined Guarantor Subsidiaries
Operating activities:
Net income									308.7	802.2	698.7
Equity in earnings of subsidiaries, net of taxes									(91.8)	(217.4)	(191.8)
Other									482.1	(33.1)	(99.0)
Net cash provided by operating activities - continuing operations									699.0	551.7	407.9
Net cash provided by operating activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by operating activities									699.0	551.7	407.9
Investing activities:
(Increase) decrease in short-term marketable securities									0.0	0.0	0.0
Proceeds from railcar lease fleet sales owned more than one year									27.3	290.6	549.2
Proceeds from disposition of property and other assets									4.1	1.9	0.0
Capital expenditures – leasing									(798.7)	(821.6)	(222.8)
Capital expenditures – manufacturing and other									(8.6)	(39.1)	(58.3)
Acquisitions, net of cash acquired									0.0	0.0	(595.6)
(Increase) decrease in investment in partially-owned subsidiaries									17.1	24.8	(4.5)
Divestitures									0.0	0.0	0.0
Other									0.8	0.2	(0.8)
Net cash required by investing activities - continuing operations									(758.0)	(543.2)	(332.8)
Net cash provided by investing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by investing activities									(758.0)	(543.2)	(332.8)
Financing activities:
Proceeds from issuance of common stock, net									0.0	0.0	0.0
Excess tax benefits from stock-based compensation									0.0	0.0	0.0
Payments to retire debt									(3.6)	(3.2)	(3.1)
Proceeds from issuance of debt									0.0	0.0	0.0
(Increase) decrease in restricted cash									0.2	(0.2)	0.0
Shares repurchased									0.0	0.0	0.0
Dividends paid to common shareholders									0.0	0.0	0.0
Purchase of shares to satisfy employee tax on vested stock									0.0	0.0	0.0
Contributions from noncontrolling interest									0.0	0.0	0.0
Contributions from controlling interest in partially-owned leasing subsidiaries									0.0	0.0	0.0
Distributions to noncontrolling interest									0.0	0.0	0.0
Distributions to controlling interest in partially-owned leasing subsidiaries									0.0	0.0	0.0
Change in intercompany financing between entities									65.9	(14.5)	(62.3)
Other									0.0	0.0	(0.7)
Net cash provided (required) by financing activities - continuing									62.5	(17.9)	(66.1)
Net cash provided (required) by financing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by financing activities									62.5	(17.9)	(66.1)
Net increase (decrease) in cash and cash equivalents									3.5	(9.4)	9.0
Cash and cash equivalents at beginning of period				1.7	1.7			11.1	1.7	11.1	2.1
Cash and cash equivalents at end of period	5.2				1.7	1.7			5.2	1.7	11.1
Reportable legal entities | Combined Non-Guarantor Subsidiaries
Operating activities:
Net income									106.5	302.5	262.4
Equity in earnings of subsidiaries, net of taxes									0.0	0.0	0.0
Other									212.3	146.4	240.1
Net cash provided by operating activities - continuing operations									318.8	448.9	502.5
Net cash provided by operating activities - discontinued									0.0	0.0	1.0
Net cash provided (required) by operating activities									318.8	448.9	503.5
Investing activities:
(Increase) decrease in short-term marketable securities									0.0	0.0	0.0
Proceeds from railcar lease fleet sales owned more than one year									10.4	267.2	140.3
Proceeds from disposition of property and other assets									11.9	6.3	22.7
Capital expenditures – leasing									(0.4)	(55.4)	(446.2)
Capital expenditures – manufacturing and other									(107.7)	(142.4)	(152.7)
Acquisitions, net of cash acquired									0.0	(46.2)	(118.8)
(Increase) decrease in investment in partially-owned subsidiaries									0.0	0.0	0.0
Divestitures									0.0	51.3	0.0
Other									6.0	0.3	0.7
Net cash required by investing activities - continuing operations									(79.8)	81.1	(554.0)
Net cash provided by investing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by investing activities									(79.8)	81.1	(554.0)
Financing activities:
Proceeds from issuance of common stock, net									0.0	0.0	0.0
Excess tax benefits from stock-based compensation									0.0	0.0	0.0
Payments to retire debt									(158.9)	(584.0)	(183.0)
Proceeds from issuance of debt									0.0	243.9	331.6
(Increase) decrease in restricted cash									13.4	43.3	13.9
Shares repurchased									0.0	0.0	0.0
Dividends paid to common shareholders									0.0	0.0	0.0
Purchase of shares to satisfy employee tax on vested stock									0.0	0.0	0.0
Contributions from noncontrolling interest									0.0	0.0	49.6
Contributions from controlling interest in partially-owned leasing subsidiaries									0.0	0.0	4.5
Distributions to noncontrolling interest									(26.4)	(39.2)	(28.2)
Distributions to controlling interest in partially-owned leasing subsidiaries									(17.1)	(24.8)	0.0
Change in intercompany financing between entities									(47.7)	(206.7)	(89.3)
Other									(2.1)	(0.8)	(1.8)
Net cash provided (required) by financing activities - continuing									(238.8)	(568.3)	97.3
Net cash provided (required) by financing activities - discontinued									0.0	0.0	(1.5)
Net cash provided (required) by financing activities									(238.8)	(568.3)	95.8
Net increase (decrease) in cash and cash equivalents									0.2	(38.3)	45.3
Cash and cash equivalents at beginning of period				51.1	51.1			89.4	51.1	89.4	44.1
Cash and cash equivalents at end of period	51.3				51.1	51.1			51.3	51.1	89.4
Eliminations
Operating activities:
Net income									(394.1)	(1,075.2)	(930.0)
Equity in earnings of subsidiaries, net of taxes									479.3	1,137.4	933.5
Other									(33.4)	(57.4)	(5.7)
Net cash provided by operating activities - continuing operations									51.8	4.8	(2.2)
Net cash provided by operating activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by operating activities									51.8	4.8	(2.2)
Investing activities:
(Increase) decrease in short-term marketable securities									0.0	0.0	0.0
Proceeds from railcar lease fleet sales owned more than one year									0.0	(43.2)	(423.7)
Proceeds from disposition of property and other assets									0.0	0.0	0.0
Capital expenditures – leasing									0.0	43.2	423.7
Capital expenditures – manufacturing and other									0.0	0.0	0.0
Acquisitions, net of cash acquired									0.0	0.0	0.0
(Increase) decrease in investment in partially-owned subsidiaries									(17.1)	(24.8)	4.5
Divestitures									0.0	0.0	0.0
Other									0.0	0.0	0.0
Net cash required by investing activities - continuing operations									(17.1)	(24.8)	4.5
Net cash provided by investing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by investing activities									(17.1)	(24.8)	4.5
Financing activities:
Proceeds from issuance of common stock, net									0.0	0.0	0.0
Excess tax benefits from stock-based compensation									0.0	0.0	0.0
Payments to retire debt									0.0	0.0	0.0
Proceeds from issuance of debt									0.0	0.0	0.0
(Increase) decrease in restricted cash									4.0	5.2	(12.9)
Shares repurchased									0.0	0.0	0.0
Dividends paid to common shareholders									0.0	0.0	0.0
Purchase of shares to satisfy employee tax on vested stock									0.0	0.0	0.0
Contributions from noncontrolling interest									0.0	0.0	0.0
Contributions from controlling interest in partially-owned leasing subsidiaries									0.0	0.0	(4.5)
Distributions to noncontrolling interest									0.0	0.0	0.0
Distributions to controlling interest in partially-owned leasing subsidiaries									17.1	24.8	0.0
Change in intercompany financing between entities									(51.7)	(4.8)	2.2
Other									0.0	0.0	0.0
Net cash provided (required) by financing activities - continuing									(30.6)	25.2	(15.2)
Net cash provided (required) by financing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by financing activities									(30.6)	25.2	(15.2)
Net increase (decrease) in cash and cash equivalents									4.1	5.2	(12.9)
Cash and cash equivalents at beginning of period				$ (35.1)	(35.1)			$ (40.3)	(35.1)	(40.3)	(27.4)
Cash and cash equivalents at end of period	$ (31.0)				$ (35.1)	$ (35.1)			$ (31.0)	$ (35.1)	$ (40.3)