Changes in Operations United States RCP&E (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	May 31, 2014	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues		$ 516,534	$ 501,002	$ 501,375	$ 482,616	$ 514,853	$ 546,299	$ 542,219	$ 397,030
Operating Income		$ 53,571	$ 91,851	$ 87,194	$ 56,996	$ 94,631	$ 117,559	$ 99,451	$ 72,620	$ 289,612	$ 384,261	$ 421,571
RCP&E [Member]
Business Acquisition, Effective Date of Acquisition	May 30, 2014
Cash consideration												218,600
Revenues												69,900
Operating Income												$ 17,200