Goodwill Schedule of Goodwill Allocated to Reporting Segments (Details) - USD ($) $ in Thousands	7 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill beginning balance		$ 452,494	$ 468,122
Goodwill acquired	$ 59,675	59,675
Effect of change in exchange rates		43,593	(15,628)
Goodwill before impairment	1,232,229	1,232,229	1,054,717	$ 1,096,660
Accumulated impairment losses	(676,467)	(676,467)	(602,223)	(628,538)
Goodwill ending balance	555,762	555,762	452,494
Electricity Operating Segment [Member]
Goodwill [Line Items]
Goodwill beginning balance		51,373	52,733
Goodwill acquired		59,675
Effect of change in exchange rates		3,193	(1,360)
Goodwill before impairment	500,625	500,625	400,299	414,910
Accumulated impairment losses	(386,384)	(386,384)	(348,926)	(362,177)
Goodwill ending balance	114,241	114,241	51,373
Gas Operating Segment [Member]
Goodwill [Line Items]
Goodwill beginning balance		319,913	331,436
Goodwill acquired		0
Effect of change in exchange rates		32,790	(11,523)
Goodwill before impairment	352,703	352,703	319,913	331,436
Accumulated impairment losses	0	0	0	0
Goodwill ending balance	352,703	352,703	319,913
Water Operating Segment [Member]
Goodwill [Line Items]
Goodwill beginning balance		81,208	83,953
Goodwill acquired		0
Effect of change in exchange rates		7,610	(2,745)
Goodwill before impairment	378,901	378,901	334,505	350,314
Accumulated impairment losses	(290,083)	(290,083)	(253,297)	$ (266,361)
Goodwill ending balance	$ 88,818	$ 88,818	$ 81,208