Goodwill Schedule of Goodwill Allocated to Reporting Segments (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill beginning balance	$ 471,648	$ 462,718	$ 500,820	$ 541,539	$ 546,437	$ 547,604	$ 500,820	$ 547,604	$ 500,820	$ 547,604	$ 500,820	$ 547,604
Goodwill acquired											4,684
Goodwill impairment	0	0	0	0	0	0	0	0	0	0	0	0	$ (174,226)
Effect of change in exchange rates											(37,382)	(46,784)
Goodwill before impairment											1,096,660	1,191,808	1,318,271
Accumulated impairment losses											(628,538)	(690,988)	(770,667)
Goodwill ending balance	$ 475,410	$ 471,648	462,718	$ 515,641	$ 541,539	546,437	471,648	541,539	475,410	515,641	468,122	500,820	547,604
Electricity Operating Segment [Member]
Goodwill [Line Items]
Goodwill beginning balance			55,687			59,258	55,687	59,258	55,687	59,258	55,687	59,258
Goodwill acquired											0
Goodwill impairment													(174,200)
Effect of change in exchange rates											(2,954)	(3,571)
Goodwill before impairment											414,910	449,668	493,610
Accumulated impairment losses											(362,177)	(393,981)	(434,352)
Goodwill ending balance											52,733	55,687	59,258
Gas Operating Segment [Member]
Goodwill [Line Items]
Goodwill beginning balance			359,485			394,878	359,485	394,878	359,485	394,878	359,485	394,878
Goodwill acquired											0
Effect of change in exchange rates											(28,049)	(35,393)
Goodwill before impairment											331,436	359,485	394,878
Accumulated impairment losses											0	0	0
Goodwill ending balance											331,436	359,485	394,878
Water Operating Segment [Member]
Goodwill [Line Items]
Goodwill beginning balance			$ 85,648			$ 93,468	$ 85,648	$ 93,468	$ 85,648	$ 93,468	85,648	93,468
Goodwill acquired											4,684
Effect of change in exchange rates											(6,379)	(7,820)
Goodwill before impairment											350,314	382,655	429,783
Accumulated impairment losses											(266,361)	(297,007)	(336,315)
Goodwill ending balance											$ 83,953	$ 85,648	$ 93,468