Restructuring Expected Costs - 2016 Projects (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring	$ 40,679	$ 587	$ 41,294	$ (8,828)
2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	65,998		65,998
Restructuring			39,998
Remaining Costs to be Recognized at Period End	26,000		26,000
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring			34,919
Employee Severance [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	44,162		44,162
Restructuring			34,662
Remaining Costs to be Recognized at Period End	9,500		9,500
Asset Impairment and Net (Gain) Loss on Sale or Disposal [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring			5,153
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	5,184		5,184
Restructuring			5,184
Remaining Costs to be Recognized at Period End	0		0
Other restructuring costs
Restructuring Cost and Reserve [Line Items]
Restructuring			1,222
Other restructuring costs | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	16,652		16,652
Restructuring			152
Remaining Costs to be Recognized at Period End	16,500		16,500
Electricity Operating Segment [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	10,044		10,044
Restructuring			6,544
Remaining Costs to be Recognized at Period End	3,500		3,500
Gas Operating Segment [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	33,214		33,214
Restructuring			20,214
Remaining Costs to be Recognized at Period End	13,000		13,000
Water Operating Segment [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	21,410		21,410
Restructuring			12,410
Remaining Costs to be Recognized at Period End	9,000		9,000
Corporate, Non-Segment [Member] | 2016 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	1,330		1,330
Restructuring			830
Remaining Costs to be Recognized at Period End	$ 500		$ 500