Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Shareholder's equity
Common stock - shares authorized (in shares)	600,000,000	275,000,000
Common stock - par value (in dollars per share)	$ 0	$ 5
Common stock - shares issued (in shares)	264,797,584	142,094,275
Westar Energy Inc [Member]
Shareholder's equity
Common stock - shares authorized (in shares)	1,000	275,000,000
Common stock - par value (in dollars per share)	$ 0.01	$ 5
Common stock - shares issued (in shares)	1	142,094,275
KCPL [Member]
Shareholder's equity
Common stock - shares authorized (in shares)	1,000	1,000
Common stock - shares issued (in shares)	1	1