Investments in Unconsolidated Affiliates (Investments in Equity Method Unconsolidated Affiliates) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	$ 1,409	$ 1,175	$ 925
Equity in earnings (losses) of unconsolidated affiliates	83	119	(15)
Electric Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	97	89	93
Equity in earnings (losses) of unconsolidated affiliates	6	5	5
Gas Utilities and Infrastructure [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	1,003	763	566
Equity in earnings (losses) of unconsolidated affiliates	27	62	19
Commercial Renewables [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	201	190	185
Equity in earnings (losses) of unconsolidated affiliates	(1)	(5)	(82)
Other [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in equity method unconsolidated affiliates	108	133	81
Equity in earnings (losses) of unconsolidated affiliates	$ 51	$ 57	$ 43