Consolidated Statements of Common Equity (Parenthetical) - $ / shares		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Stockholders' Equity [Abstract]
Common stock dividends (in dollars per share)	[1]	$ 1.175	$ 1.10	$ 1.02

[1] Amounts reflect the effects of a two-for-one common stock split distributed in May 2016.