Restructuring Restructuring Expected Costs, Costs To-Date, Remaining Costs, and Costs During the Period - 2014 Projects (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Costs recognized during the period ended	$ (5,447)	$ 5,524
2014 Project [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	59,790
Restructuring and Related Cost, Cost Incurred to Date			55,800
Costs recognized during the period ended	(5,447)
Remaining Costs to be Recognized at Period End	9,437
2014 Project [Member] | Employee severance costs
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	41,431
Restructuring and Related Cost, Cost Incurred to Date			47,447
Costs recognized during the period ended	(6,016)
Remaining Costs to be Recognized at Period End	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
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
2014 Project [Member] | Other restructuring costs
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	10,140
Restructuring and Related Cost, Cost Incurred to Date			401
Costs recognized during the period ended	302
Remaining Costs to be Recognized at Period End	9,437
2014 Project [Member] | Electricity Operating Segment [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	35,316
Restructuring and Related Cost, Cost Incurred to Date			29,660
Costs recognized during the period ended	(3,127)
Remaining Costs to be Recognized at Period End	8,783
2014 Project [Member] | Gas Operating Segment [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	12,918
Restructuring and Related Cost, Cost Incurred to Date			12,185
Costs recognized during the period ended	502
Remaining Costs to be Recognized at Period End	231
2014 Project [Member] | Water Operating Segment [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	1,249
Restructuring and Related Cost, Cost Incurred to Date			1,106
Costs recognized during the period ended	117
Remaining Costs to be Recognized at Period End	26
2014 Project [Member] | Corporate Unallocated [Member]
Restructuring Cost and Reserve [Line Items]
Total expected costs at period end	10,307
Restructuring and Related Cost, Cost Incurred to Date			12,849
Costs recognized during the period ended	(2,939)
Remaining Costs to be Recognized at Period End	$ 397