Segment Reporting (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 segment	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting
Number of operating segments			4
Segment reporting
Total revenues	$ 138,466,000	$ 139,293,000	$ 276,075,000	$ 271,343,000
Income (loss) before income tax expense (benefit)	16,688,000	10,770,000	35,108,000	21,722,000
Identifiable assets	3,629,991,000	2,874,539,000	3,629,991,000	2,874,539,000	2,209,887,000
Facility closing expense		1,600,000
Restructuring accruals recorded in 2012 and 2011
Segment reporting
Reduction in previously recorded restructuring accruals			1,600,000
U.S. Operations
Segment reporting
Total revenues	77,324,000	84,601,000	152,991,000	165,844,000
Income (loss) before income tax expense (benefit)	4,645,000	4,561,000	9,493,000	10,301,000
Identifiable assets	984,027,000	1,181,004,000	984,027,000	1,181,004,000
Canadian Operations
Segment reporting
Total revenues	17,911,000	20,105,000	37,247,000	38,649,000
Income (loss) before income tax expense (benefit)	3,544,000	3,795,000	8,103,000	6,371,000
Identifiable assets	106,834,000	95,218,000	106,834,000	95,218,000
European Operations
Segment reporting
Total revenues	31,096,000	21,794,000	63,928,000	42,744,000
Income (loss) before income tax expense (benefit)	8,707,000	2,820,000	19,449,000	6,321,000
Identifiable assets	1,970,703,000	997,609,000	1,970,703,000	997,609,000
Asia Pacific Operations
Segment reporting
Total revenues	12,135,000	12,793,000	21,909,000	24,106,000
Income (loss) before income tax expense (benefit)	(208,000)	(406,000)	(1,937,000)	(1,271,000)
Identifiable assets	$ 568,427,000	$ 600,708,000	$ 568,427,000	$ 600,708,000