Financial Statements for Guarantors of the Senior Notes (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income (loss)	$ 146.3	$ 156.9	$ 173.1	$ 233.0	$ 119.3	$ 106.1	$ 88.2	$ 78.8	$ 709.3	$ 392.4	$ 253.7
Adjustments to reconcile net income to net cash:
Income from discontinued operations	0.1	(0.6)	0.2	0.3	(0.4)	(0.3)	1.0	(6.6)	0	(6.3)	(1.8)
Depreciation and amortization									244.6	211.5	193.7
Stock-based compensation expense									53.3	44.5	27.7
Excess tax benefits from stock-based compensation									(24.4)	(8.5)	(0.6)
Provision (benefit) for deferred income taxes									(5.8)	45.8	126.3
Net gains on railcar lease fleet sales owned more than one year at the time of sale									(92.3)	(20.4)	(33.5)
Gains on disposition of property, plant, and equipment									(12.1)	(0.8)	(5.0)
Non-cash interest expense									30.7	30.8	31.2
Changes in assets and liabilities:
(Increase) decrease in receivables									(56.4)	17.2	2.7
(Increase) decrease in inventories									(186.3)	(95.6)	(128.0)
(Increase) decrease in restricted cash									25.0	(25.0)	0
(Increase) decrease in other assets									(8.3)	(29.1)	(41.5)
Increase (decrease) in accounts payable									60.7	29.0	(16.7)
Increase (decrease) in accrued liabilities									82.1	72.4	125.5
Increase (decrease) in other liabilities									2.6	8.2	(3.9)
Equity in earnings of subsidiaries, net of taxes									0	0	0
Other									(4.5)	(6.4)	(3.2)
Net cash provided (required) by operating activities - continuing									818.2	659.7	526.6
Net cash provided by operating activities - discontinued									1.0	2.5	0.8
Net cash provided (required) by operating activities									819.2	662.2	527.4
Investing activities:
(Increase) decrease in short-term marketable securities									74.7	(149.7)	0
Proceeds from railcar lease fleet sales									265.8	131.6	126.3
Proceeds from railcar lease fleet sales – sale and leaseback									0	0	58.3
Proceeds from disposition of property, plant, equipment, and other assets									23.0	3.7	16.8
Capital expenditures – leasing									(245.3)	(581.1)	(352.6)
Capital expenditures – manufacturing and other									(219.3)	(149.9)	(116.6)
Acquisitions, net of cash acquired									(714.4)	(73.2)	(46.2)
(Increase) decrease in investment in partially-owned subsidiaries									0	0
Other									0.8	0	1.7
Net cash provided (required) by investing activities - continuing									(814.7)	(818.6)	(312.3)
Net cash provided (required) by investing activities - discontinued									0	0.6	0.9
Net cash provided (required) by investing activities									(814.7)	(818.0)	(311.4)
Financing activities:
Proceeds from issuance of common stock, net									0.6	2.5	4.1
Excess tax benefits from stock-based compensation									24.4	8.5	0.6
Payments to retire debt									(186.6)	(262.1)	(378.4)
Proceeds from issuance of debt									727.3	175.0	443.8
(Increase) decrease in restricted cash									1.0	(12.5)	17.1
Shares repurchased									(36.5)	(103.2)	(45.2)
Dividends paid to common shareholders									(54.4)	(39.3)	(31.7)
Purchase of shares to satisfy employee tax on vested stock									(38.3)	(9.6)	(4.8)
Proceeds from sale of interests in partially-owned leasing subsidiaries									0	296.7	0
Repurchase of noncontrolling interests in partially-owned leasing subsidiary									0	(84.0)	0
Contributions from noncontrolling interest									49.6	50.0	0
Distributions to noncontrolling interest									(28.2)	(10.0)	0
Distributions to controlling interest in partially-owned subsidiaries										0
Contributions from controlling interest in partially-owned subs									0
Change in intercompany financing between entities									0	0	0
Other									(2.5)	0.8	(0.5)
Net cash provided (required) by financing activities - continuing									456.4	12.8	5.0
Net cash required by financing activities - discontinued									(1.5)	(1.5)	0.9
Net cash provided (required) by financing activities									454.9	11.3	5.9
Net increase (decrease) in cash and cash equivalents									459.4	(144.5)	221.9
Cash and cash equivalents at beginning of period				428.5				573.0	428.5	573.0	351.1
Cash and cash equivalents at end of period	887.9				428.5				887.9	428.5	573.0
Parent
Operating activities:
Net income (loss)									678.2	375.5	255.2
Adjustments to reconcile net income to net cash:
Income from discontinued operations									0	0	0
Depreciation and amortization									6.1	4.5	3.9
Stock-based compensation expense									53.3	44.5	27.7
Excess tax benefits from stock-based compensation									(24.4)	(8.5)	(0.6)
Provision (benefit) for deferred income taxes									(4.0)	43.3	4.9
Net gains on railcar lease fleet sales owned more than one year at the time of sale									0	0	0
Gains on disposition of property, plant, and equipment									1.4	(0.3)	(0.4)
Non-cash interest expense									15.7	14.4	13.3
Changes in assets and liabilities:
(Increase) decrease in receivables									(50.9)	1.0	(7.8)
(Increase) decrease in inventories									0	0	0
(Increase) decrease in restricted cash									0	0	0
(Increase) decrease in other assets									(38.8)	146.8	(30.2)
Increase (decrease) in accounts payable									3.4	0.1	3.5
Increase (decrease) in accrued liabilities									2.1	61.8	5.9
Increase (decrease) in other liabilities									9.2	(45.4)	(12.8)
Equity in earnings of subsidiaries, net of taxes									(740.2)	(378.3)	(246.6)
Other									(0.4)	(1.8)	0.9
Net cash provided (required) by operating activities - continuing									(89.3)	257.6	16.9
Net cash provided by operating activities - discontinued									0	0	0
Net cash provided (required) by operating activities									(89.3)	257.6	16.9
Investing activities:
(Increase) decrease in short-term marketable securities									74.7	(149.7)
Proceeds from railcar lease fleet sales									0	0	0
Proceeds from railcar lease fleet sales – sale and leaseback											0
Proceeds from disposition of property, plant, equipment, and other assets									0.4	0	0
Capital expenditures – leasing									0	0	0
Capital expenditures – manufacturing and other									(9.2)	(23.7)	(6.6)
Acquisitions, net of cash acquired									0	0	0
(Increase) decrease in investment in partially-owned subsidiaries									0	0
Other									0.9	108.8	0
Net cash provided (required) by investing activities - continuing									66.8	(64.6)	(6.6)
Net cash provided (required) by investing activities - discontinued									0	0	0
Net cash provided (required) by investing activities									66.8	(64.6)	(6.6)
Financing activities:
Proceeds from issuance of common stock, net									0.6	2.5	4.1
Excess tax benefits from stock-based compensation									24.4	8.5	0.6
Payments to retire debt									(0.5)	0	0
Proceeds from issuance of debt									395.7	0	0
(Increase) decrease in restricted cash									0	0	0
Shares repurchased									(36.5)	(103.2)	(45.2)
Dividends paid to common shareholders									(54.4)	(39.3)	(31.7)
Purchase of shares to satisfy employee tax on vested stock									(38.3)	(9.6)	(4.8)
Proceeds from sale of interests in partially-owned leasing subsidiaries										0
Repurchase of noncontrolling interests in partially-owned leasing subsidiary										0
Contributions from noncontrolling interest									0	0
Distributions to noncontrolling interest									0	0
Distributions to controlling interest in partially-owned subsidiaries										0
Contributions from controlling interest in partially-owned subs									0
Change in intercompany financing between entities									149.4	(148.3)	236.5
Other									0	0	0
Net cash provided (required) by financing activities - continuing									440.4	(289.4)	159.5
Net cash required by financing activities - discontinued									0	0	0
Net cash provided (required) by financing activities									440.4	(289.4)	159.5
Net increase (decrease) in cash and cash equivalents									417.9	(96.4)	169.8
Cash and cash equivalents at beginning of period				409.8				506.2	409.8	506.2	336.4
Cash and cash equivalents at end of period	827.7				409.8				827.7	409.8	506.2
Combined Guarantor Subsidiaries
Operating activities:
Net income (loss)									727.1	378.7	227.7
Adjustments to reconcile net income to net cash:
Income from discontinued operations									0.1	(6.3)	(1.4)
Depreciation and amortization									24.9	31.5	30.4
Stock-based compensation expense									18.9	15.9	10.2
Excess tax benefits from stock-based compensation									0	0	0
Provision (benefit) for deferred income taxes									(8.9)	(5.3)	125.5
Net gains on railcar lease fleet sales owned more than one year at the time of sale									(41.4)	(10.9)	(9.0)
Gains on disposition of property, plant, and equipment									0	0	(0.4)
Non-cash interest expense									(1.9)	(0.9)	0.3
Changes in assets and liabilities:
(Increase) decrease in receivables									33.4	27.6	10.1
(Increase) decrease in inventories									(194.5)	(103.7)	(106.3)
(Increase) decrease in restricted cash									25.0	(25.0)	0
(Increase) decrease in other assets									13.2	9.3	(2.7)
Increase (decrease) in accounts payable									39.2	15.0	(26.0)
Increase (decrease) in accrued liabilities									72.8	20.5	109.5
Increase (decrease) in other liabilities									(0.2)	4.7	(33.7)
Equity in earnings of subsidiaries, net of taxes									(228.9)	(97.1)	(88.2)
Other									(3.5)	(4.4)	(3.2)
Net cash provided (required) by operating activities - continuing									475.3	249.6	242.8
Net cash provided by operating activities - discontinued									1.0	2.5	0.8
Net cash provided (required) by operating activities									476.3	252.1	243.6
Investing activities:
(Increase) decrease in short-term marketable securities									0	0
Proceeds from railcar lease fleet sales									549.2	322.4	527.6
Proceeds from railcar lease fleet sales – sale and leaseback											58.3
Proceeds from disposition of property, plant, equipment, and other assets									0	0.3	13.6
Capital expenditures – leasing									(222.8)	(545.6)	(380.9)
Capital expenditures – manufacturing and other									(64.0)	(34.1)	(38.8)
Acquisitions, net of cash acquired									0	35.6	2.1
(Increase) decrease in investment in partially-owned subsidiaries									(4.5)	47.3
Other									(0.8)	0	0
Net cash provided (required) by investing activities - continuing									257.1	(174.1)	181.9
Net cash provided (required) by investing activities - discontinued									0	0.6	0.9
Net cash provided (required) by investing activities									257.1	(173.5)	182.8
Financing activities:
Proceeds from issuance of common stock, net									0	0	0
Excess tax benefits from stock-based compensation									0	0	0
Payments to retire debt									(3.1)	(52.2)	(8.9)
Proceeds from issuance of debt									0	0	0
(Increase) decrease in restricted cash									0	0	0
Shares repurchased									0	0	0
Dividends paid to common shareholders									0	0	0
Purchase of shares to satisfy employee tax on vested stock									0	0	0
Proceeds from sale of interests in partially-owned leasing subsidiaries										0
Repurchase of noncontrolling interests in partially-owned leasing subsidiary										(84.0)
Contributions from noncontrolling interest									0	0
Distributions to noncontrolling interest									0	0
Distributions to controlling interest in partially-owned subsidiaries										0
Contributions from controlling interest in partially-owned subs									0
Change in intercompany financing between entities									(719.1)	56.7	(415.4)
Other									(0.7)	0	0
Net cash provided (required) by financing activities - continuing									(722.9)	(79.5)	(424.3)
Net cash required by financing activities - discontinued									(1.5)	(1.5)	0.9
Net cash provided (required) by financing activities									(724.4)	(81.0)	(423.4)
Net increase (decrease) in cash and cash equivalents									9.0	(2.4)	3.0
Cash and cash equivalents at beginning of period				2.1				4.5	2.1	4.5	1.5
Cash and cash equivalents at end of period	11.1				2.1				11.1	2.1	4.5
Combined Non-Guarantor Subsidiaries
Operating activities:
Net income (loss)									265.0	109.8	97.2
Adjustments to reconcile net income to net cash:
Income from discontinued operations									(0.1)	0	(0.4)
Depreciation and amortization									213.6	175.5	159.4
Stock-based compensation expense									13.4	7.5	4.1
Excess tax benefits from stock-based compensation									0	0	0
Provision (benefit) for deferred income taxes									7.1	7.8	(4.1)
Net gains on railcar lease fleet sales owned more than one year at the time of sale									(50.9)	(9.5)	(24.5)
Gains on disposition of property, plant, and equipment									(13.5)	(0.5)	(4.2)
Non-cash interest expense									16.9	17.3	17.6
Changes in assets and liabilities:
(Increase) decrease in receivables									(38.7)	(12.0)	0.4
(Increase) decrease in inventories									(1.7)	6.4	(24.9)
(Increase) decrease in restricted cash									0	0	0
(Increase) decrease in other assets									(4.2)	(3.0)	(3.3)
Increase (decrease) in accounts payable									18.1	14.4	5.8
Increase (decrease) in accrued liabilities									12.1	(9.9)	6.2
Increase (decrease) in other liabilities									(6.4)	(22.7)	(1.4)
Equity in earnings of subsidiaries, net of taxes									0	0	0
Other									(0.6)	(0.2)	(0.9)
Net cash provided (required) by operating activities - continuing									430.1	280.9	227.0
Net cash provided by operating activities - discontinued									0	0	0
Net cash provided (required) by operating activities									430.1	280.9	227.0
Investing activities:
(Increase) decrease in short-term marketable securities									0	0
Proceeds from railcar lease fleet sales									140.3	57.1	88.7
Proceeds from railcar lease fleet sales – sale and leaseback											0
Proceeds from disposition of property, plant, equipment, and other assets									22.6	3.4	3.2
Capital expenditures – leasing									(446.2)	(283.4)	(461.7)
Capital expenditures – manufacturing and other									(146.1)	(92.1)	(71.2)
Acquisitions, net of cash acquired									(714.4)	(108.8)	(48.3)
(Increase) decrease in investment in partially-owned subsidiaries									0	0
Other									0.7	0	1.7
Net cash provided (required) by investing activities - continuing									(1,143.1)	(423.8)	(487.6)
Net cash provided (required) by investing activities - discontinued									0	0	0
Net cash provided (required) by investing activities									(1,143.1)	(423.8)	(487.6)
Financing activities:
Proceeds from issuance of common stock, net									0	0	0
Excess tax benefits from stock-based compensation									0	0	0
Payments to retire debt									(183.0)	(318.7)	(369.5)
Proceeds from issuance of debt									331.6	175.0	443.8
(Increase) decrease in restricted cash									13.9	2.5	(6.0)
Shares repurchased									0	0	0
Dividends paid to common shareholders									0	0	0
Purchase of shares to satisfy employee tax on vested stock									0	0	0
Proceeds from sale of interests in partially-owned leasing subsidiaries										296.7
Repurchase of noncontrolling interests in partially-owned leasing subsidiary										0
Contributions from noncontrolling interest									49.6	50.0
Distributions to noncontrolling interest									(28.2)	(10.0)
Distributions to controlling interest in partially-owned subsidiaries										(47.3)
Contributions from controlling interest in partially-owned subs									4.5
Change in intercompany financing between entities									571.8	(36.8)	218.8
Other									(1.8)	0.8	(0.5)
Net cash provided (required) by financing activities - continuing									758.4	112.2	286.6
Net cash required by financing activities - discontinued									0	0	0
Net cash provided (required) by financing activities									758.4	112.2	286.6
Net increase (decrease) in cash and cash equivalents									45.4	(30.7)	26.0
Cash and cash equivalents at beginning of period				44.0				74.7	44.0	74.7	48.7
Cash and cash equivalents at end of period	89.4				44.0				89.4	44.0	74.7
Eliminations
Operating activities:
Net income (loss)									(961.0)	(471.6)	(326.4)
Adjustments to reconcile net income to net cash:
Income from discontinued operations									0	0	0
Depreciation and amortization									0	0	0
Stock-based compensation expense									(32.3)	(23.4)	(14.3)
Excess tax benefits from stock-based compensation									0	0	0
Provision (benefit) for deferred income taxes									0	0	0
Net gains on railcar lease fleet sales owned more than one year at the time of sale									0	0	0
Gains on disposition of property, plant, and equipment									0	0	0
Non-cash interest expense									0	0	0
Changes in assets and liabilities:
(Increase) decrease in receivables									(0.2)	0.6	0
(Increase) decrease in inventories									9.9	1.7	3.2
(Increase) decrease in restricted cash									0	0	0
(Increase) decrease in other assets									21.5	(182.2)	(5.3)
Increase (decrease) in accounts payable									0	(0.5)	0
Increase (decrease) in accrued liabilities									(4.9)	0	3.9
Increase (decrease) in other liabilities									0	71.6	44.0
Equity in earnings of subsidiaries, net of taxes									969.1	475.4	334.8
Other									0	0	0
Net cash provided (required) by operating activities - continuing									2.1	(128.4)	39.9
Net cash provided by operating activities - discontinued									0	0	0
Net cash provided (required) by operating activities									2.1	(128.4)	39.9
Investing activities:
(Increase) decrease in short-term marketable securities									0	0
Proceeds from railcar lease fleet sales									(423.7)	(247.9)	(490.0)
Proceeds from railcar lease fleet sales – sale and leaseback											0
Proceeds from disposition of property, plant, equipment, and other assets									0	0	0
Capital expenditures – leasing									423.7	247.9	490.0
Capital expenditures – manufacturing and other									0	0	0
Acquisitions, net of cash acquired									0	0	0
(Increase) decrease in investment in partially-owned subsidiaries									4.5	(47.3)
Other									0	(108.8)	0
Net cash provided (required) by investing activities - continuing									4.5	(156.1)	0
Net cash provided (required) by investing activities - discontinued									0	0	0
Net cash provided (required) by investing activities									4.5	(156.1)	0
Financing activities:
Proceeds from issuance of common stock, net									0	0	0
Excess tax benefits from stock-based compensation									0	0	0
Payments to retire debt									0	108.8	0
Proceeds from issuance of debt									0	0	0
(Increase) decrease in restricted cash									(12.9)	(15.0)	23.1
Shares repurchased									0	0	0
Dividends paid to common shareholders									0	0	0
Purchase of shares to satisfy employee tax on vested stock									0	0	0
Proceeds from sale of interests in partially-owned leasing subsidiaries										0
Repurchase of noncontrolling interests in partially-owned leasing subsidiary										0
Contributions from noncontrolling interest									0
Distributions to noncontrolling interest									0
Distributions to controlling interest in partially-owned subsidiaries										47.3
Contributions from controlling interest in partially-owned subs									(4.5)
Change in intercompany financing between entities									(2.1)	128.4	(39.9)
Other									0	0	0
Net cash provided (required) by financing activities - continuing									(19.5)	269.5	(16.8)
Net cash required by financing activities - discontinued									0	0	0
Net cash provided (required) by financing activities									(19.5)	269.5	(16.8)
Net increase (decrease) in cash and cash equivalents									(12.9)	(15.0)	23.1
Cash and cash equivalents at beginning of period				(27.4)				(12.4)	(27.4)	(12.4)	(35.5)
Cash and cash equivalents at end of period	$ (40.3)				$ (27.4)				$ (40.3)	$ (27.4)	$ (12.4)