Restructuring Restructuring Expected Costs - 2018 Projects (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring	$ 666	$ (678)	$ 82,908	$ 7,417
2018 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	101,140		101,140
Restructuring			83,064
Restructuring and Related Cost, Expected Cost Remaining	18,076		18,076
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring			79,011
Employee Severance [Member] | 2018 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	81,669		81,669
Restructuring			81,669
Restructuring and Related Cost, Expected Cost Remaining	0		0
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring			3,329
Other Restructuring [Member] | 2018 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	19,356		19,356
Restructuring			1,280
Restructuring and Related Cost, Expected Cost Remaining	18,076		18,076
Asset Impairment and Net (Gain) Loss on Sale or Disposal [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring			568
Asset Impairment and Net (Gain) Loss on Sale or Disposal [Member] | 2018 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	115		115
Restructuring			115
Restructuring and Related Cost, Expected Cost Remaining	0		0
Electricity Operating Segment [Member] | 2018 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	20,609		20,609
Restructuring			19,109
Restructuring and Related Cost, Expected Cost Remaining	1,500		1,500
Gas Operating Segment [Member] | 2018 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	52,289		52,289
Restructuring			41,583
Restructuring and Related Cost, Expected Cost Remaining	10,706		10,706
Water Operating Segment [Member] | 2018 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	21,804		21,804
Restructuring			15,934
Restructuring and Related Cost, Expected Cost Remaining	5,870		5,870
Corporate, Non-Segment [Member] | 2018 Projects [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	6,438		6,438
Restructuring			6,438
Restructuring and Related Cost, Expected Cost Remaining	$ 0		$ 0