Restructuring Expected Costs - 2016 Projects (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring	$ 3,052	$ 2,237
2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	67,846
Restructuring and Related Cost, Cost Incurred to Date			$ 47,794
Restructuring	3,052
Remaining Costs to be Recognized at Period End	17,000
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring	1,316
Employee Severance [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	45,502
Restructuring and Related Cost, Cost Incurred to Date			39,686
Restructuring	1,316
Remaining Costs to be Recognized at Period End	4,500
Asset Impairment and Net (Gain) Loss on Sale or Disposal [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring	0
Asset Impairment and Net (Gain) Loss on Sale or Disposal [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	7,219
Restructuring and Related Cost, Cost Incurred to Date			7,219
Restructuring	0
Remaining Costs to be Recognized at Period End	0
Other restructuring costs
Restructuring Cost and Reserve [Line Items]
Restructuring	1,736
Other restructuring costs | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	15,125
Restructuring and Related Cost, Cost Incurred to Date			889
Restructuring	1,736
Remaining Costs to be Recognized at Period End	12,500
Electricity Operating Segment [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	10,151
Restructuring and Related Cost, Cost Incurred to Date			8,827
Restructuring	(176)
Remaining Costs to be Recognized at Period End	1,500
Gas Operating Segment [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	33,552
Restructuring and Related Cost, Cost Incurred to Date			23,968
Restructuring	1,084
Remaining Costs to be Recognized at Period End	8,500
Water Operating Segment [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	20,579
Restructuring and Related Cost, Cost Incurred to Date			13,061
Restructuring	1,018
Remaining Costs to be Recognized at Period End	6,500
Corporate, Non-Segment [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	3,564
Restructuring and Related Cost, Cost Incurred to Date			$ 1,938
Restructuring	1,126
Remaining Costs to be Recognized at Period End	$ 500