Significant Accounting Policies (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 item	Dec. 31, 2012	Dec. 31, 2011
Information about the operations in different geographical areas
Number of facilities through which services are provided									30
Revenues
Revenue	$ 152,179	$ 134,973	$ 140,105	$ 132,352	$ 157,848	$ 140,993	$ 142,794	$ 139,456	$ 559,609	$ 581,091	$ 614,270
Property, plant and equipment
Net property, plant and equipment	40,711				44,091				40,711	44,091
United States
Revenues
Revenue									469,596	492,118	523,381
Property, plant and equipment
Net property, plant and equipment	34,556				37,587				34,556	37,587
Other countries
Information about the operations in different geographical areas
Number of facilities through which services are provided									10
Revenues
Revenue									90,013	88,973	90,889
Property, plant and equipment
Net property, plant and equipment	$ 6,155				$ 6,504				$ 6,155	$ 6,504