Segments and Related Information (Schedule of Financial Information by Reportable Segment - Assets) (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets:
Assets		$ 3,183,132	$ 2,927,347	$ 3,550,800
Reportable Segments [Member] | Communications [Member]
Assets:
Assets		1,156,900	1,032,200	1,197,400
Reportable Segments [Member] | Oil and Gas [Member]
Assets:
Assets		1,267,200	1,131,400	1,389,500
Reportable Segments [Member] | Electrical Transmission [Member]
Assets:
Assets		419,100	409,100	489,500
Reportable Segments [Member] | Power Generation and Industrial [Member]
Assets:
Assets		268,100	252,500	340,100
Reportable Segments [Member] | Other [Member]
Assets:
Assets		27,700	34,300	24,600
Corporate [Member]
Assets:
Assets	[1]	$ 44,100	$ 67,800	$ 109,700

[1] Corporate segment assets as of December 31, 2015 and 2014 have been recast to reflect the adoption of ASU 2015-03, as discussed in Note 7 - Debt. For the Years Ended December 31,Capital Expenditures:2016 2015 2014Communications$28.5 $25.8 $23.4Oil and Gas64.0 38.1 44.2Electrical Transmission19.8 13.0 25.8Power Generation and Industrial3.4 3.5 6.7Other0.3 0.2 —Corporate1.1 3.8 9.2Consolidated capital expenditures$117.1 $84.4 $109.3