Business Combinations and Segment Information - Total assets by business segment (Details 2) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Assets	$ 1,868,907	$ 1,818,683
Corporate
Segment Reporting Information [Line Items]
Assets	37,432	42,312
Discontinued Operations
Segment Reporting Information [Line Items]
Assets	249
Electric | Operating Segments
Segment Reporting Information [Line Items]
Assets	1,575,790	1,520,887
Manufacturing | Operating Segments
Segment Reporting Information [Line Items]
Assets	168,705	173,860
Plastics | Operating Segments
Segment Reporting Information [Line Items]
Assets	$ 86,731	$ 81,624