Quarterly Information (Unaudited) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended						12 Months Ended
	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information [Line Items]
Tax benefit, net							$ (22,942)	$ (91,784)	$ (11,957)
Change in enacted tax rate, non-cash tax benefit	$ 120,100						120,100
Restructuring charges			$ 1,400	$ 4,700	$ 5,100	$ 4,100
Share-Based Compensation [Member]
Quarterly Financial Information [Line Items]
Tax benefit, net	$ 5,600						5,400
Contracts Accounted for under Percentage-of-Completion [Member] | Canadian Dollars [Member] | Joint Venture [Member] | Pacer [Member] | Other [Member]
Quarterly Financial Information [Line Items]
Project losses		$ 7,000		$ 5,100			$ 7,900	$ 5,100	$ 16,300