Nuclear Plant (Tables)

6 Months Ended

Jun. 30, 2017

Nuclear Plant [Abstract]

Changes in nuclear decommissioning trust fund

The following table summarizes the change in Great Plains Energy's and KCP&L's nuclear decommissioning trust fund.

	June 30			December 31
	2017			2016
Decommissioning Trust		(millions)
Beginning balance January 1		$	222.9		$	200.7
Contributions		1.6			3.3
Earned income, net of fees		2.0			4.1
Net realized gains		0.3			0.3
Net unrealized gains		11.6			14.5
Ending balance		$	238.4		$	222.9

Detail of assets held in nuclear decommissioning trust fund

The nuclear decommissioning trust is reported at fair value on the balance sheets and is invested in assets as detailed in the following table.

	June 30, 2017												December 31, 2016
	Cost Basis		Unrealized Gains			Unrealized Losses				Fair Value			Cost Basis			Unrealized Gains			Unrealized Losses				Fair Value
	(millions)
Equity securities	$	94.3		$	72.3		$	(0.8	)		$	165.8		$	93.3		$	62.1		$	(1.5	)		$	153.9
Debt securities	67.0			2.8			(0.3		)		69.5			63.4			2.3			(0.5		)		65.2
Other	3.1			—			—				3.1			3.8			—			—				3.8
Total	$	164.4		$	75.1		$	(1.1	)		$	238.4		$	160.5		$	64.4		$	(2.0	)		$	222.9

Gains and losses from the sale of securities by the nuclear decommissioning trust fund

The following table summarizes the realized gains and losses from the sale of securities in the nuclear decommissioning trust fund.

	Three Months Ended June 30					Year to Date June 30
	2017		2016			2017			2016
	(millions)
Realized gains	$	0.1	$	0.2		$	0.4		$	0.9
Realized losses	—		(0.3		)	(0.1		)	(1.0		)