Business Segment Information (Summary of Identifiable Assets) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Total assets	$ 3,560,637	$ 3,592,020
Contracting Services [Member]
Total assets	1,869,593	1,856,016
Production Facilities [Member]
Total assets	518,220	512,990
Oil and Gas [Member]
Total assets	$ 1,172,824	$ 1,223,014