Geographic Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Reportable_Segments	Jun. 30, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of reportable segments			1
External Revenues	$ 47,716	$ 42,267	$ 91,543	$ 82,317
Disclosure on Geographic Areas, Long-Lived Assets in Foreign Countries	420,877	334,579	420,877	334,579
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
External Revenues			64,726	58,827
Disclosure on Geographic Areas, Long-Lived Assets in Foreign Countries	315,847	245,051	315,847	245,051
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
External Revenues			2,253	445
Disclosure on Geographic Areas, Long-Lived Assets in Foreign Countries	8,925	0	8,925	0
Latin America
Revenues from External Customers and Long-Lived Assets [Line Items]
External Revenues			4,338	4,779
Disclosure on Geographic Areas, Long-Lived Assets in Foreign Countries	12,632	18,664	12,632	18,664
Australia
Revenues from External Customers and Long-Lived Assets [Line Items]
External Revenues			17,557	16,156
Disclosure on Geographic Areas, Long-Lived Assets in Foreign Countries	1,401	1,458	1,401	1,458
Singapore
Revenues from External Customers and Long-Lived Assets [Line Items]
External Revenues			1,620	1,357
Disclosure on Geographic Areas, Long-Lived Assets in Foreign Countries	71,456	61,959	71,456	61,959
New Zealand
Revenues from External Customers and Long-Lived Assets [Line Items]
External Revenues			1,026	753
Disclosure on Geographic Areas, Long-Lived Assets in Foreign Countries	240	202	240	202
India
Revenues from External Customers and Long-Lived Assets [Line Items]
External Revenues			23	0
Disclosure on Geographic Areas, Long-Lived Assets in Foreign Countries	$ 10,376	$ 7,245	$ 10,376	$ 7,245