Schedule of Goodwill Allocated to Reporting Segments (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	$ 1,232,229
Accumulated impairment losses, at beginning of period	(676,467)
Goodwill, net, at beginning of period	555,762
Goodwill acquired	572,870
Effect of change in exchange rates	(9,223)
Goodwill before impairment, at end of period	1,781,059
Accumulated impairment losses, at end of period	(661,650)
Goodwill, net, at end of period	555,762	$ 1,119,409
Electricity Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	500,625
Accumulated impairment losses, at beginning of period	(386,384)
Goodwill, net, at beginning of period	114,241
Goodwill acquired	0
Effect of change in exchange rates	(706)
Goodwill before impairment, at end of period	492,367
Accumulated impairment losses, at end of period	(378,832)
Goodwill, net, at end of period	114,241	113,535
Gas Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	352,703
Accumulated impairment losses, at beginning of period	0
Goodwill, net, at beginning of period	352,703
Goodwill acquired	0
Effect of change in exchange rates	(6,669)
Goodwill before impairment, at end of period	346,034
Accumulated impairment losses, at end of period	0
Goodwill, net, at end of period	352,703	346,034
Water Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	378,901
Accumulated impairment losses, at beginning of period	(290,083)
Goodwill, net, at beginning of period	88,818
Goodwill acquired	0
Effect of change in exchange rates	(1,605)
Goodwill before impairment, at end of period	370,031
Accumulated impairment losses, at end of period	(282,818)
Goodwill, net, at end of period	88,818	87,213
Networks Operating Segment [Member]
Goodwill [Roll Forward]
Goodwill before impairment, at beginning of period	0
Accumulated impairment losses, at beginning of period	0
Goodwill, net, at beginning of period	0
Goodwill acquired	572,870
Effect of change in exchange rates	(243)
Goodwill before impairment, at end of period	572,627
Accumulated impairment losses, at end of period	0
Goodwill, net, at end of period	$ 0	$ 572,627