Restructuring Restructuring Expected Costs, Costs To-Date, Remaining Costs, and Costs During the Period - 2014 Projects (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Costs recognized during the period ended	$ (4,234)	$ (7,793)	$ (9,681)	$ (2,269)
Employee severance costs
Restructuring Cost and Reserve [Line Items]
Costs recognized during the period ended			(11,659)
Asset Impairment and Net (Gain) Loss on Sale or Disposal [Member]
Restructuring Cost and Reserve [Line Items]
Costs recognized during the period ended			267
Other restructuring costs
Restructuring Cost and Reserve [Line Items]
Costs recognized during the period ended			1,711
2014 Project [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	55,350		55,350
Restructuring and Related Cost, Cost Incurred to Date					$ 55,800
Costs recognized during the period ended			(9,681)
Remaining Costs to be Recognized at Period End	9,231		9,231
2014 Project [Member] | Employee severance costs
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	35,788		35,788
Restructuring and Related Cost, Cost Incurred to Date					47,447
Costs recognized during the period ended			(11,659)
Remaining Costs to be Recognized at Period End	0		0
2014 Project [Member] | Asset Impairment and Net (Gain) Loss on Sale or Disposal [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	8,219		8,219
Restructuring and Related Cost, Cost Incurred to Date					7,952
Costs recognized during the period ended			267
Remaining Costs to be Recognized at Period End	0		0
2014 Project [Member] | Other restructuring costs
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	11,343		11,343
Restructuring and Related Cost, Cost Incurred to Date					401
Costs recognized during the period ended			1,711
Remaining Costs to be Recognized at Period End	9,231		9,231
2014 Project [Member] | Electricity Operating Segment [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	32,440		32,440
Restructuring and Related Cost, Cost Incurred to Date					29,660
Costs recognized during the period ended			(5,830)
Remaining Costs to be Recognized at Period End	8,610		8,610
2014 Project [Member] | Gas Operating Segment [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	11,727		11,727
Restructuring and Related Cost, Cost Incurred to Date					12,185
Costs recognized during the period ended			(684)
Remaining Costs to be Recognized at Period End	226		226
2014 Project [Member] | Water Operating Segment [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	1,405		1,405
Restructuring and Related Cost, Cost Incurred to Date					1,106
Costs recognized during the period ended			273
Remaining Costs to be Recognized at Period End	26		26
2014 Project [Member] | Corporate Unallocated [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	9,778		9,778
Restructuring and Related Cost, Cost Incurred to Date					$ 12,849
Costs recognized during the period ended			(3,440)
Remaining Costs to be Recognized at Period End	$ 369		$ 369