Financial Statements for Guarantors of the Senior Notes (Details 3) - 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
Operating activities:
Net income	$ 204.0	$ 212.2	$ 220.8	$ 189.0	$ 146.3	$ 156.9	$ 173.1	$ 233.0	$ 826.0	$ 709.3	$ 392.4
Equity in earnings of subsidiaries, net of taxes									0.0	0.0	0.0
Other									113.7	108.9	267.3
Net cash provided by operating activities - continuing operations									939.7	818.2	659.7
Net cash provided by operating activities - discontinued									0.0	1.0	2.5
Net cash provided (required) by operating activities									939.7	819.2	662.2
Investing activities:
(Increase) decrease in short-term marketable securities									(9.9)	74.7	(149.7)
Proceeds from railcar lease fleet sales owned more than one year									514.6	265.8	131.6
Proceeds from disposition of property and other assets									8.2	23.0	3.7
Capital expenditures – leasing									(833.8)	(245.3)	(581.1)
Capital expenditures – manufacturing and other									(196.0)	(219.3)	(149.9)
Acquisitions, net of cash acquired									(46.2)	(714.4)	(73.2)
(Increase) decrease in investment in partially-owned subsidiaries									0.0	0.0	0.0
Divestitures									51.3	0.0	0.0
Other									0.5	0.8	0.0
Net cash required by investing activities - continuing operations									(511.3)	(814.7)	(818.6)
Net cash provided (required) by investing activities - discontinued									0.0	0.0	0.6
Net cash provided (required) by investing activities									(511.3)	(814.7)	(818.0)
Financing activities:
Proceeds from issuance of common stock, net									0.3	0.6	2.5
Excess tax benefits from stock-based compensation									13.3	24.4	8.5
Payments to retire debt									(587.2)	(186.6)	(262.1)
Proceeds from issuance of debt									242.4	727.3	175.0
(Increase) decrease in restricted cash									48.3	1.0	(12.5)
Shares repurchased									(115.0)	(36.5)	(103.2)
Dividends paid to common shareholders									(64.9)	(54.4)	(39.3)
Purchase of shares to satisfy employee tax on vested stock									(27.5)	(38.3)	(9.6)
Proceeds from sale of interests in partially-owned leasing subsidiaries									0.0	0.0	296.7
Proceeds from sale of interests in partially-owned leasing subsidiaries									0.0	0.0	(84.0)
Contributions from noncontrolling interest									0.0	49.6	50.0
Contributions from controlling interest in partially-owned leasing subsidiaries									0.0	0.0	0.0
Distributions to noncontrolling interest									(39.2)	(28.2)	(10.0)
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									(0.8)	(2.5)	0.8
Net cash provided (required) by financing activities - continuing									(530.3)	456.4	12.8
Net cash required by financing activities - discontinued									0.0	(1.5)	(1.5)
Net cash provided (required) by financing activities									(530.3)	454.9	11.3
Net increase (decrease) in cash and cash equivalents									(101.9)	459.4	(144.5)
Cash and cash equivalents at beginning of period				887.9				428.5	887.9	428.5	573.0
Cash and cash equivalents at end of period	786.0				887.9				786.0	887.9	428.5
Reportable legal entities | Parent
Operating activities:
Net income									796.5	678.2	375.5
Equity in earnings of subsidiaries, net of taxes									(920.0)	(741.7)	(378.6)
Other									57.8	(26.5)	260.6
Net cash provided by operating activities - continuing operations									(65.7)	(90.0)	257.5
Net cash provided by operating activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by operating activities									(65.7)	(90.0)	257.5
Investing activities:
(Increase) decrease in short-term marketable securities									(9.9)	74.7	(149.7)
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	0.3	0.0
Capital expenditures – leasing									0.0	0.0	0.0
Capital expenditures – manufacturing and other									(14.5)	(8.3)	(23.7)
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	0.9	108.8
Net cash required by investing activities - continuing operations									(24.4)	67.6	(64.6)
Net cash provided (required) by investing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by investing activities									(24.4)	67.6	(64.6)
Financing activities:
Proceeds from issuance of common stock, net									0.3	0.6	2.5
Excess tax benefits from stock-based compensation									13.3	24.4	8.5
Payments to retire debt									0.0	(0.5)	0.0
Proceeds from issuance of debt									(1.5)	395.7	0.0
(Increase) decrease in restricted cash									0.0	0.0	0.0
Shares repurchased									(115.0)	(36.5)	(103.2)
Dividends paid to common shareholders									(64.9)	(54.4)	(39.3)
Purchase of shares to satisfy employee tax on vested stock									(27.5)	(38.3)	(9.6)
Proceeds from sale of interests in partially-owned leasing subsidiaries									0.0	0.0	0.0
Proceeds from sale of interests in partially-owned leasing subsidiaries									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									226.0	149.4	(148.3)
Other									0.0	0.0	0.0
Net cash provided (required) by financing activities - continuing									30.7	440.4	(289.4)
Net cash required by financing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by financing activities									30.7	440.4	(289.4)
Net increase (decrease) in cash and cash equivalents									(59.4)	418.0	(96.5)
Cash and cash equivalents at beginning of period				827.7				409.7	827.7	409.7	506.2
Cash and cash equivalents at end of period	768.3				827.7				768.3	827.7	409.7
Reportable legal entities | Combined Guarantor Subsidiaries
Operating activities:
Net income									802.2	698.7	348.1
Equity in earnings of subsidiaries, net of taxes									(217.4)	(191.8)	(84.6)
Other									(33.1)	(99.0)	(79.7)
Net cash provided by operating activities - continuing operations									551.7	407.9	183.8
Net cash provided by operating activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by operating activities									551.7	407.9	183.8
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									290.6	549.2	322.4
Proceeds from disposition of property and other assets									1.9	0.0	0.1
Capital expenditures – leasing									(821.6)	(222.8)	(545.6)
Capital expenditures – manufacturing and other									(39.1)	(58.3)	(53.6)
Acquisitions, net of cash acquired									0.0	(595.6)	0.0
(Increase) decrease in investment in partially-owned subsidiaries									24.8	(4.5)	47.3
Divestitures									0.0	0.0	0.0
Other									0.2	(0.8)	0.0
Net cash required by investing activities - continuing operations									(543.2)	(332.8)	(229.4)
Net cash provided (required) by investing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by investing activities									(543.2)	(332.8)	(229.4)
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									(3.2)	(3.1)	(52.2)
Proceeds from issuance of debt									0.0	0.0	0.0
(Increase) decrease in restricted cash									(0.2)	0.0	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
Proceeds from sale of interests in partially-owned leasing subsidiaries									0.0	0.0	0.0
Proceeds from sale of interests in partially-owned leasing subsidiaries									0.0	0.0	(84.0)
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									(14.5)	(62.3)	179.5
Other									0.0	(0.7)	0.0
Net cash provided (required) by financing activities - continuing									(17.9)	(66.1)	43.3
Net cash required by financing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by financing activities									(17.9)	(66.1)	43.3
Net increase (decrease) in cash and cash equivalents									(9.4)	9.0	(2.3)
Cash and cash equivalents at beginning of period				11.1				2.1	11.1	2.1	4.4
Cash and cash equivalents at end of period	1.7				11.1				1.7	11.1	2.1
Reportable legal entities | Combined Non-Guarantor Subsidiaries
Operating activities:
Net income									302.5	262.4	128.3
Equity in earnings of subsidiaries, net of taxes									0.0	0.0	0.0
Other									146.4	240.1	218.7
Net cash provided by operating activities - continuing operations									448.9	502.5	347.0
Net cash provided by operating activities - discontinued									0.0	1.0	2.5
Net cash provided (required) by operating activities									448.9	503.5	349.5
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									267.2	140.3	57.1
Proceeds from disposition of property and other assets									6.3	22.7	3.6
Capital expenditures – leasing									(55.4)	(446.2)	(283.4)
Capital expenditures – manufacturing and other									(142.4)	(152.7)	(72.6)
Acquisitions, net of cash acquired									(46.2)	(118.8)	(73.2)
(Increase) decrease in investment in partially-owned subsidiaries									0.0	0.0	0.0
Divestitures									51.3	0.0	0.0
Other									0.3	0.7	0.0
Net cash required by investing activities - continuing operations									81.1	(554.0)	(368.5)
Net cash provided (required) by investing activities - discontinued									0.0	0.0	0.6
Net cash provided (required) by investing activities									81.1	(554.0)	(367.9)
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									(584.0)	(183.0)	(318.7)
Proceeds from issuance of debt									243.9	331.6	175.0
(Increase) decrease in restricted cash									43.3	13.9	2.5
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
Proceeds from sale of interests in partially-owned leasing subsidiaries									0.0	0.0	296.7
Proceeds from sale of interests in partially-owned leasing subsidiaries									0.0	0.0	0.0
Contributions from noncontrolling interest									0.0	49.6	50.0
Contributions from controlling interest in partially-owned leasing subsidiaries									0.0	4.5	0.0
Distributions to noncontrolling interest									(39.2)	(28.2)	(10.0)
Distributions to controlling interest in partially-owned leasing subsidiaries									(24.8)	0.0	(47.3)
Change in intercompany financing between entities									(206.7)	(89.3)	(159.8)
Other									(0.8)	(1.8)	0.8
Net cash provided (required) by financing activities - continuing									(568.3)	97.3	(10.8)
Net cash required by financing activities - discontinued									0.0	(1.5)	(1.5)
Net cash provided (required) by financing activities									(568.3)	95.8	(12.3)
Net increase (decrease) in cash and cash equivalents									(38.3)	45.3	(30.7)
Cash and cash equivalents at beginning of period				89.4				44.1	89.4	44.1	74.8
Cash and cash equivalents at end of period	51.1				89.4				51.1	89.4	44.1
Eliminations
Operating activities:
Net income									(1,075.2)	(930.0)	(459.5)
Equity in earnings of subsidiaries, net of taxes									1,137.4	933.5	463.2
Other									(57.4)	(5.7)	(132.3)
Net cash provided by operating activities - continuing operations									4.8	(2.2)	(128.6)
Net cash provided by operating activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by operating activities									4.8	(2.2)	(128.6)
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									(43.2)	(423.7)	(247.9)
Proceeds from disposition of property and other assets									0.0	0.0	0.0
Capital expenditures – leasing									43.2	423.7	247.9
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									(24.8)	4.5	(47.3)
Divestitures									0.0	0.0	0.0
Other									0.0	0.0	(108.8)
Net cash required by investing activities - continuing operations									(24.8)	4.5	(156.1)
Net cash provided (required) by investing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by investing activities									(24.8)	4.5	(156.1)
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	108.8
Proceeds from issuance of debt									0.0	0.0	0.0
(Increase) decrease in restricted cash									5.2	(12.9)	(15.0)
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
Proceeds from sale of interests in partially-owned leasing subsidiaries									0.0	0.0	0.0
Proceeds from sale of interests in partially-owned leasing subsidiaries									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	(4.5)	0.0
Distributions to noncontrolling interest									0.0	0.0	0.0
Distributions to controlling interest in partially-owned leasing subsidiaries									24.8	0.0	47.3
Change in intercompany financing between entities									(4.8)	2.2	128.6
Other									0.0	0.0	0.0
Net cash provided (required) by financing activities - continuing									25.2	(15.2)	269.7
Net cash required by financing activities - discontinued									0.0	0.0	0.0
Net cash provided (required) by financing activities									25.2	(15.2)	269.7
Net increase (decrease) in cash and cash equivalents									5.2	(12.9)	(15.0)
Cash and cash equivalents at beginning of period				$ (40.3)				$ (27.4)	(40.3)	(27.4)	(12.4)
Cash and cash equivalents at end of period	$ (35.1)				$ (40.3)				$ (35.1)	$ (40.3)	$ (27.4)