Segment Information (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of customers worldwide	6,000
Number of geographic regions	3
Revenues	$ 691,243
Long-lived assets	1,170,958
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	368,700	333,700	232,800
Long-lived assets	$ 918,400	$ 864,700