Operating Segment and Sales and Credit Concentrations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 segment	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Number of Reportable Segments			3
Total revenues	$ 237,509	$ 159,404	$ 419,624	$ 354,514
Earnings from operations	51,850	39,869	88,357	71,098
Total Assets	977,880		977,880		825,609
Manufacturing [Member]
Segment Reporting Information [Line Items]
Total revenues	267,669	177,325	485,661	405,708
Earnings from operations	64,224	42,906	117,609	86,667
Total Assets	306,654		306,654		298,951
Railcar Leasing [Member]
Segment Reporting Information [Line Items]
Total revenues	13,885	7,527	25,631	14,070
Earnings from operations	7,335	3,653	13,596	5,820
Total Assets	602,637		602,637		478,000
Railcar Services [Member]
Segment Reporting Information [Line Items]
Total revenues	17,312	19,681	33,850	35,322
Earnings from operations	3,126	4,042	5,345	6,390
Total Assets	55,020		55,020		52,150
Corporate And Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(61,357)	(45,129)	(125,518)	(100,586)
Earnings from operations	(22,835)	(10,732)	(48,193)	(27,779)
Total Assets	13,569		13,569		(3,492)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	237,509	159,404	419,624	354,514
Earnings from operations	51,850	39,869	88,357	71,098
Operating Segments [Member] | Manufacturing [Member]
Segment Reporting Information [Line Items]
Total revenues	206,364	132,242	360,327	305,217
Earnings from operations	44,597	32,780	78,252	66,759
Operating Segments [Member] | Railcar Leasing [Member]
Segment Reporting Information [Line Items]
Total revenues	13,885	7,527	25,631	14,070
Earnings from operations	7,399	3,645	13,629	5,808
Operating Segments [Member] | Railcar Services [Member]
Segment Reporting Information [Line Items]
Total revenues	17,260	19,635	33,666	35,227
Earnings from operations	3,116	4,083	5,297	6,388
Operating Segments [Member] | Corporate And Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Earnings from operations	(3,262)	(639)	(8,821)	(7,857)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Earnings from operations	0	0	0	0
Intersegment Eliminations [Member] | Manufacturing [Member]
Segment Reporting Information [Line Items]
Total revenues	61,305	45,083	125,334	100,491
Earnings from operations	19,627	10,126	39,357	19,908
Intersegment Eliminations [Member] | Railcar Leasing [Member]
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Earnings from operations	(64)	8	(33)	12
Intersegment Eliminations [Member] | Railcar Services [Member]
Segment Reporting Information [Line Items]
Total revenues	52	46	184	95
Earnings from operations	10	(41)	48	2
Intersegment Eliminations [Member] | Corporate And Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(61,357)	(45,129)	(125,518)	(100,586)
Earnings from operations	$ (19,573)	$ (10,093)	$ (39,372)	$ (19,922)