Business Segment Information - Summary of financial information concerning reportable segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 1,263,840	$ 2,337,413	$ 1,861,489
Operating profit (loss)	(156,277)	400,929	277,439
Capital expenditures	167,426	371,502	201,681
Depreciation and amortization	270,977	230,813	213,128
Identifiable assets	1,237,094	1,759,358	1,383,860
Operating Segments | Technical Services
Segment Reporting Information [Line Items]
Revenues	1,175,293	2,180,457	1,729,732
Operating profit (loss)	(132,982)	390,004	276,246
Capital expenditures	155,361	342,932	167,586
Depreciation and amortization	237,778	198,636	181,026
Identifiable assets	976,761	1,514,084	1,113,877
Operating Segments | Support Services
Segment Reporting Information [Line Items]
Revenues	88,547	156,956	131,757
Operating profit (loss)	(2,363)	42,510	26,223
Capital expenditures	11,055	27,148	32,250
Depreciation and amortization	32,697	31,578	31,417
Identifiable assets	$ 108,262	$ 157,688	$ 202,243
Corporate
Segment Reporting Information [Line Items]
Revenues
Operating profit (loss)	$ (14,515)	$ (16,113)	$ (15,659)
Capital expenditures	1,010	1,422	1,845
Depreciation and amortization	502	599	685
Identifiable assets	$ 152,071	$ 87,586	$ 67,740
Loss on disposition of assets, net
Segment Reporting Information [Line Items]
Revenues
Operating profit (loss)	$ (6,417)	$ (15,472)	$ (9,371)
Capital expenditures
Depreciation and amortization
Identifiable assets