Schedule of Goodwill Allocated to Reporting Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2017
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	$ 1,054,717
Accumulated impairment losses, at beginning of period	(602,223)
Goodwill, net, at beginning of period	452,494
Effect of change in exchange rates	10,412
Goodwill before impairment, at end of period	1,082,689
Accumulated impairment losses, at end of period	(619,783)
Goodwill, net, at end of period	452,494	$ 462,906
Electricity Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	400,299
Accumulated impairment losses, at beginning of period	(348,926)
Goodwill, net, at beginning of period	51,373
Effect of change in exchange rates	776
Goodwill before impairment, at end of period	409,960
Accumulated impairment losses, at end of period	(357,811)
Goodwill, net, at end of period	51,373	52,149
Gas Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	319,913
Accumulated impairment losses, at beginning of period	0
Goodwill, net, at beginning of period	319,913
Effect of change in exchange rates	7,774
Goodwill before impairment, at end of period	327,687
Accumulated impairment losses, at end of period	0
Goodwill, net, at end of period	319,913	327,687
Water Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	334,505
Accumulated impairment losses, at beginning of period	(253,297)
Goodwill, net, at beginning of period	81,208
Effect of change in exchange rates	1,862
Goodwill before impairment, at end of period	345,042
Accumulated impairment losses, at end of period	(261,972)
Goodwill, net, at end of period	$ 81,208	$ 83,070