Goodwill Schedule of Goodwill Allocated to Reporting Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Goodwill beginning balance	$ 468,122	$ 500,820
Goodwill acquired		4,684
Effect of change in exchange rates	(15,628)	(37,382)
Goodwill before impairment	1,054,717	1,096,660	$ 1,191,808
Accumulated impairment losses	(602,223)	(628,538)	(690,988)
Goodwill ending balance	452,494	468,122
Electricity Operating Segment [Member]
Goodwill [Line Items]
Goodwill beginning balance	52,733	55,687
Goodwill acquired		0
Effect of change in exchange rates	(1,360)	(2,954)
Goodwill before impairment	400,299	414,910	449,668
Accumulated impairment losses	(348,926)	(362,177)	(393,981)
Goodwill ending balance	51,373	52,733
Gas Operating Segment [Member]
Goodwill [Line Items]
Goodwill beginning balance	331,436	359,485
Goodwill acquired		0
Effect of change in exchange rates	(11,523)	(28,049)
Goodwill before impairment	319,913	331,436	359,485
Accumulated impairment losses	0	0	0
Goodwill ending balance	319,913	331,436
Water Operating Segment [Member]
Goodwill [Line Items]
Goodwill beginning balance	83,953	85,648
Goodwill acquired		4,684
Effect of change in exchange rates	(2,745)	(6,379)
Goodwill before impairment	334,505	350,314	382,655
Accumulated impairment losses	(253,297)	(266,361)	$ (297,007)
Goodwill ending balance	$ 81,208	$ 83,953