Schedule of Goodwill Allocated to Reporting Segments (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2016 USD ($)
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	$ 1,096,660
Accumulated impairment losses, at beginning of period	(628,538)
Goodwill, net, at beginning of period	468,122
Effect of change in exchange rates	7,583
Goodwill before impairment, at end of period	1,117,212
Accumulated impairment losses, at end of period	(641,507)
Goodwill, net, at end of period	475,705
Electricity Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	414,910
Accumulated impairment losses, at beginning of period	(362,177)
Goodwill, net, at beginning of period	52,733
Effect of change in exchange rates	329
Goodwill before impairment, at end of period	421,852
Accumulated impairment losses, at end of period	(368,790)
Goodwill, net, at end of period	53,062
Gas Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	331,436
Accumulated impairment losses, at beginning of period	0
Goodwill, net, at beginning of period	331,436
Effect of change in exchange rates	5,843
Goodwill before impairment, at end of period	337,279
Accumulated impairment losses, at end of period	0
Goodwill, net, at end of period	337,279
Water Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	350,314
Accumulated impairment losses, at beginning of period	(266,361)
Goodwill, net, at beginning of period	83,953
Effect of change in exchange rates	1,411
Goodwill before impairment, at end of period	358,081
Accumulated impairment losses, at end of period	(272,717)
Goodwill, net, at end of period	$ 85,364