Financings and Capitalization (Issuance of Common Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	May 31, 2018	Jun. 30, 2017
Debt Disclosure [Abstract]
Number of shares issued (in shares)	638,898	1,494,371
Average price per share (in dollars per share)	$ 45.83	$ 47.31
Common stock issued	$ 29	$ 70