Operating Segments and Sales, Geographic and Credit Concentrations (Details 2) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($) customer	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) customer	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) Segment customer	Dec. 31, 2014 USD ($) customer	Dec. 31, 2013 USD ($) customer
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 1,530,155				$ 1,192,409				$ 1,530,155	$ 1,192,409	$ 825,609
Revenue, Net	$ 260,895	$ 172,667	$ 191,998	$ 263,776	$ 150,540	$ 162,842	$ 237,509	$ 182,115	$ 889,336	$ 733,006	$ 750,592
Number of reportable segments | Segment									3
Foreign Operations [Member]
Operating Segment and Sales and Credit Concentrations (Textual) [Abstract]
Percentage of revenue from company's foreign operations									4.90%	4.20%	2.00%
Percentage of foreign assets of the total consolidated assets	0.80%				1.00%				0.80%	1.00%
Sales Revenue, Segment [Member] | IELP Entities [Member]
Operating Segment and Sales and Credit Concentrations (Textual) [Abstract]
Percentage of revenue from significant customer									29.20%	31.00%	31.70%
Railcar Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 56,880				$ 52,639				$ 56,880	$ 52,639	$ 52,150
Revenue, Net									$ 74,497	$ 67,842	$ 72,854
Operating Segment and Sales and Credit Concentrations (Textual) [Abstract]
Percentage of revenue from affiliates									2.80%	2.60%	2.30%
Number of customers that made up more than 10% of consolidated revenues | customer									0	0	0
Number of customers that made up more than 10% of consolidated accounts receivable | customer	0				0				0	0
Railcar Leasing [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 1,195,261				$ 908,010				$ 1,195,261	$ 908,010	$ 478,000
Revenue, Net									$ 116,714	$ 65,108	$ 31,871
Operating Segment and Sales and Credit Concentrations (Textual) [Abstract]
Percentage of revenue from affiliates									0.00%	0.00%	0.00%
Number of customers that made up more than 10% of consolidated revenues | customer									0	0	0
Number of customers that made up more than 10% of consolidated accounts receivable | customer	0				0				0	0
Manufacturing [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 272,721				$ 318,157				$ 272,721	$ 318,157	$ 264,689
Revenue, Net									$ 1,019,460	$ 1,019,621	$ 864,022
Operating Segment and Sales and Credit Concentrations (Textual) [Abstract]
Percentage of revenue from affiliates									30.30%	33.50%	33.40%
Manufacturing [Member] | Accounts Receivable [Member]
Operating Segment and Sales and Credit Concentrations (Textual) [Abstract]
Manufacturing receivables from significant customers	20.90%				60.50%				20.90%	60.50%
Corporate And Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 5,293				$ (86,397)				$ 5,293	$ (86,397)	$ 30,770