Geographic Information (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues from external customers
Total revenues	$ 563,340,000	$ 659,200,000	$ 114,424,000	$ 73,662,000	$ 65,524,000	$ 23,795,000	$ 31,622,000	$ 22,429,000	$ 1,410,626,000	$ 143,370,000	$ 101,889,000
Percentage of total net book value of the entity's property and equipment	98.00%				98.00%				98.00%	98.00%
United States
Revenues from external customers
Total revenues									1,389,568,000	143,370,000	101,889,000
Property and equipment	109,500,000				55,600,000				109,500,000	55,600,000
Belgium
Revenues from external customers
Total revenues									20,289,000
Canada
Revenues from external customers
Total revenues									769,000
Outside of the United States
Revenues from external customers
Total revenues									21,058,000
United Kingdom
Revenues from external customers
Property and equipment	$ 21,400,000				$ 15,300,000				$ 21,400,000	$ 15,300,000