Evergy (EVRG) 10-K 22 Feb 19 2018 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 15, 2019	Jun. 30, 2018
Entity information [Abstract]
Entity Registrant Name	EVERGY, INC.
Entity Central Index Key	1,711,269
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		254,630,033
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 15,236,578,926
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	false

Consolidated Statements of Inco

Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
OPERATING REVENUES	$ 4,275.9	$ 2,571	$ 2,562.1
OPERATING EXPENSES:
Fuel and purchased power	1,078.7	541.5	509.5
SPP network transmission costs	259.9	247.9	232.8
Operating and maintenance	1,115.8	563.5	587.2
Depreciation and amortization	618.8	371.7	338.5
Taxes other than income tax	269.1	167.6	191.7
Total Operating Expenses	3,342.3	1,892.2	1,859.7
INCOME FROM OPERATIONS	933.6	678.8	702.4
OTHER INCOME (EXPENSE):
Investment earnings	8.8	4	2.5
Other income	15.5	8.3	34.6
Other expense	(78.7)	(39.1)	(38.6)
Total Other Income (Expense), Net	(54.4)	(26.8)	(1.5)
Interest expense	279.6	171	161.7
INCOME BEFORE INCOME TAXES	599.6	481	539.2
Income tax expense	59	151.2	184.5
Equity in earnings of equity method investees, net of income taxes	5.4	6.7	6.5
NET INCOME	546	336.5	361.2
Less: Net income attributable to noncontrolling interests	10.2	12.6	14.6
Net Income (Loss) Attributable to Parent	$ 535.8	$ 323.9	$ 346.6
Basic earnings per common share (in dollars per share)	$ 2.50	$ 2.27	$ 2.43
Diluted earnings per common share (in dollars per share)	$ 2.50	$ 2.27	$ 2.43
Weighted Average Number of Shares Outstanding, Basic	213.9	142.5	142.1
Average number of diluted common shares outstanding (in shares)	214.1	142.6	142.5
COMPREHENSIVE INCOME
Net income	$ 546	$ 336.5	$ 361.2
Derivative hedging activity
Gain (loss) on derivative hedging instruments	(5.4)	0	0
Income tax benefit (expense) on derivative hedging instruments	1.4	0	0
Net gain (loss) on derivative hedging instruments	(4)	0	0
Derivative hedging activity, net of tax	(4)	0	0
Defined benefit pension plans
Net gain (loss) arising during period	1.4	0	0
Income tax benefit benefit (expense)	(0.4)	0	0
Net gain (loss) arising during period, net of tax	1	0	0
Change in unrecognized pension expense, net of tax	(1)	0	0
Total other comprehensive income	(3)	0	0
Total comprehensive income, net of tax, including portion attributable to noncontrolling interest	543	336.5	361.2
Total comprehensive income, net of tax, attributable to noncontrolling interest	10.2	12.6	14.6
Comprehensive income (loss)	532.8	323.9	346.6
Westar Energy Inc [Member]
OPERATING REVENUES	2,614.9	2,571	2,562.1
OPERATING EXPENSES:
Fuel and purchased power	599.2	541.5	509.5
SPP network transmission costs	259.9	247.9	232.8
Operating and maintenance	640.7	563.5	587.2
Depreciation and amortization	390.9	371.7	338.5
Taxes other than income tax	173.7	167.6	191.7
Total Operating Expenses	2,064.4	1,892.2	1,859.7
INCOME FROM OPERATIONS	550.5	678.8	702.4
OTHER INCOME (EXPENSE):
Investment earnings	(0.6)	4	2.5
Other income	13.9	8.3	34.6
Other expense	(46.8)	(39.1)	(38.6)
Total Other Income (Expense), Net	(33.5)	(26.8)	(1.5)
Interest expense	176.8	171	161.7
INCOME BEFORE INCOME TAXES	340.2	481	539.2
Income tax expense	(4.3)	151.2	184.5
Equity in earnings of equity method investees, net of income taxes	4.6	6.7	6.5
NET INCOME	349.1	336.5	361.2
Less: Net income attributable to noncontrolling interests	10.2	12.6	14.6
Net Income (Loss) Attributable to Parent	338.9	323.9	346.6
COMPREHENSIVE INCOME
Net income	349.1	336.5	361.2
KCPL [Member]
OPERATING REVENUES	1,823.1	1,890.7	1,875.4
OPERATING EXPENSES:
Fuel and purchased power	520.6	480.7	429.1
Operating and maintenance	494.2	474.8	502
Depreciation and amortization	281.3	266.3	247.5
Taxes other than income tax	117.2	182.5	177.5
Total Operating Expenses	1,413.3	1,404.3	1,356.1
INCOME FROM OPERATIONS	409.8	486.4	519.3
OTHER INCOME (EXPENSE):
Investment earnings	2.8	2	0.6
Other income	2.2	9.2	11.2
Other expense	(30.9)	(50.8)	(44.8)
Total Other Income (Expense), Net	(25.9)	(39.6)	(33)
Interest expense	133.7	138.8	139.4
INCOME BEFORE INCOME TAXES	250.2	308	346.9
Income tax expense	87.3	128.2	121.9
NET INCOME	162.9	179.8	225
Net Income (Loss) Attributable to Parent	162.9	179.8	225
COMPREHENSIVE INCOME
Net income	162.9	179.8	225
Derivative hedging activity
Reclassification to expenses, net of tax	3.7	4.6	5.4
Derivative hedging activity, net of tax	3.7	4.6	5.4
Defined benefit pension plans
Total other comprehensive income	3.7	4.6	5.4
Comprehensive income (loss)	$ 166.6	$ 184.4	$ 230.4

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 160.3	$ 3.4
Receivables, net	193.7	290.7
Accounts receivable pledged as collateral	365	0
Fuel inventory and supplies	511	293.6
Income taxes receivable	68	0
Regulatory assets	303.9	99.5
Prepaid expenses and other assets	79.1	39.8
Total Current Assets	1,681	727
PROPERTY, PLANT AND EQUIPMENT, NET	18,782.5	9,553.8
OTHER ASSETS:
Regulatory assets	1,757.9	685.4
Nuclear decommissioning trust fund	472.1	237.1
Goodwill	2,338.9	0
Other	396.5	244.8
Total Other Assets	4,965.4	1,167.3
TOTAL ASSETS	25,598.1	11,624.4
CURRENT LIABILITIES:
Current maturities of long-term debt	705.4	0
Notes payable and commercial paper	738.6	275.7
Collateralized note payable	365	0
Accounts payable	451.5	204.2
Accrued dividends	0	53.8
Accrued taxes	133.6	87.7
Accrued interest	110.9	72.7
Regulatory liabilities	110.2	11.6
Asset retirement obligations	49.8	25.1
Other	171.9	64.4
Total Current Liabilities	2,867.2	823.7
LONG-TERM LIABILITIES:
Long-term debt, net	6,636.3	3,687.6
Deferred income taxes	1,599.2	815.7
Unamortized investment tax credits	373.2	257.1
Regulatory liabilities	2,218.8	1,094
Pension and post-retirement liability	987.6	491.2
Asset retirement obligations	637.3	380
Other	236.7	133.3
Total Long-Term Liabilities	12,740.2	6,940.3
Commitments and Contingencies (Note 14)
Shareholders' Equity:
Common stock	8,685.2	2,734.8
Retained earnings	1,346	1,173.3
Accumulated other comprehensive income	(3)	0
Shareholders' Equity	10,028.2	3,908.1
Noncontrolling Interests	(37.5)	(47.7)
Total Equity	9,990.7	3,860.4
TOTAL LIABILITIES AND EQUITY	25,598.1	11,624.4
Westar Energy Inc [Member]
CURRENT ASSETS:
Cash and cash equivalents	44.5	3.4
Receivables, net	84.3	290.7
Related party receivables	2.6	0
Accounts receivable pledged as collateral	185	0
Fuel inventory and supplies	276.8	293.6
Income taxes receivable	42.7	0
Regulatory assets	97.1	99.5
Prepaid expenses and other assets	35	39.8
Total Current Assets	768	727
PROPERTY, PLANT AND EQUIPMENT, NET	9,718.3	9,553.8
OTHER ASSETS:
Regulatory assets	700.4	685.4
Nuclear decommissioning trust fund	227.5	237.1
Other	233.4	244.8
Total Other Assets	1,161.3	1,167.3
TOTAL ASSETS	11,816.8	11,624.4
CURRENT LIABILITIES:
Current maturities of long-term debt	300	0
Notes payable and commercial paper	411.7	275.7
Collateralized note payable	185	0
Accounts payable	154.4	204.2
Related party payables	14.9	0
Accrued dividends	0	53.8
Accrued taxes	88.6	87.7
Accrued interest	74.4	72.7
Regulatory liabilities	19.5	11.6
Asset retirement obligations	17.1	25.1
Other	83	64.4
Total Current Liabilities	1,378.9	823.7
LONG-TERM LIABILITIES:
Long-term debt, net	3,389.8	3,687.6
Deferred income taxes	815.4	815.7
Unamortized investment tax credits	249.7	257.1
Regulatory liabilities	1,101.8	1,094
Pension and post-retirement liability	474.7	491.2
Asset retirement obligations	264	380
Other	130.7	133.3
Total Long-Term Liabilities	6,477.2	6,940.3
Commitments and Contingencies (Note 14)
Shareholders' Equity:
Common stock	2,737.6	2,734.8
Retained earnings	1,260.6	1,173.3
Shareholders' Equity	3,998.2	3,908.1
Noncontrolling Interests	(37.5)	(47.7)
Total Equity	3,960.7	3,860.4
TOTAL LIABILITIES AND EQUITY	11,816.8	11,624.4
KCPL [Member]
CURRENT ASSETS:
Cash and cash equivalents	2.6	2.2
Receivables, net	62.7	106.3
Related party receivables	101.8	84.7
Accounts receivable pledged as collateral	130	130
Fuel inventory and supplies	177.6	197
Income taxes receivable	0	5.4
Regulatory assets	130.9	153.6
Prepaid expenses and other assets	36.9	27.6
Total Current Assets	642.5	706.8
PROPERTY, PLANT AND EQUIPMENT, NET	6,688.1	6,565.6
OTHER ASSETS:
Regulatory assets	495.2	545.1
Nuclear decommissioning trust fund	244.6	258.4
Other	50.1	48
Total Other Assets	789.9	851.5
TOTAL ASSETS	8,120.5	8,123.9
CURRENT LIABILITIES:
Current maturities of long-term debt	400	350
Notes payable and commercial paper	176.9	167.5
Collateralized note payable	130	130
Accounts payable	211.1	249
Accrued taxes	39.7	29
Accrued interest	28.9	32.4
Regulatory liabilities	52.8	8.3
Asset retirement obligations	29.2	34.9
Other	69.7	63.4
Total Current Liabilities	1,138.3	1,064.5
LONG-TERM LIABILITIES:
Long-term debt, net	2,130.1	2,232.2
Deferred income taxes	631.8	616.1
Unamortized investment tax credits	120.7	121.8
Regulatory liabilities	794.3	770.9
Pension and post-retirement liability	491.9	512.2
Asset retirement obligations	231.8	231.4
Other	81.8	61.6
Total Long-Term Liabilities	4,482.4	4,546.2
Commitments and Contingencies (Note 14)
Shareholders' Equity:
Common stock	1,563.1	1,563.1
Retained earnings	932.6	949.7
Accumulated other comprehensive income	4.1	0.4
Shareholders' Equity	2,499.8	2,513.2
Total Equity	2,499.8	2,513.2
TOTAL LIABILITIES AND EQUITY	8,120.5	8,123.9
Variable Interest Entities [Member]
CURRENT ASSETS:
PROPERTY, PLANT AND EQUIPMENT, NET	169.2	176.3
CURRENT LIABILITIES:
Current maturities of long-term debt	30.3	28.5
Accrued interest	0.5	0.7
LONG-TERM LIABILITIES:
Long-term debt, net	51.1	81.4
Variable Interest Entities [Member] | Westar Energy Inc [Member]
CURRENT ASSETS:
PROPERTY, PLANT AND EQUIPMENT, NET	169.2	176.3
CURRENT LIABILITIES:
Current maturities of long-term debt	30.3	28.5
Accrued interest	0.5	0.7
LONG-TERM LIABILITIES:
Long-term debt, net	$ 51.1	$ 81.4

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 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)	255,326,252	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

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash and cash equivalents	$ 160.3	$ 3.4
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income	546	336.5	$ 361.2
Adjustments to reconcile income to net cash from operating activities:
Depreciation and amortization	618.8	371.7	338.5
Amortization of nuclear fuel	43.6	32.2	26.7
Amortization of deferred refueling outage	21.2	16.1	18.4
Amortization of deferred regulatory gain from sale leaseback	(5.5)	(5.5)	(5.5)
Amortization of corporate-owned life insurance	22.6	20.6	18
Non-cash compensation	29.9	8.8	9.3
Net deferred income taxes and credits	124.2	149.6	185.2
Allowance for equity funds used during construction	(3.1)	(2)	(11.6)
Payments for asset retirement obligations	(22.4)	(16)	(5.4)
Equity in earnings of equity method investees, net of income taxes	(5.4)	(6.7)	(6.5)
Other	(2)	(6)	(22)
Changes in working capital items:
Accounts receivable	265.1	(2.1)	(30.3)
Accounts receivable pledged as collateral	(185)	0	0
Fuel inventory and supplies	54.7	7.2	1.8
Prepaid expenses and other current assets	(128.1)	55.8	(18.3)
Accounts payable	56.7	10	(8.1)
Accrued taxes	(76.4)	9.2	(5.9)
Other current liabilities	92	(118)	(86.4)
Changes in other assets	66.8	32	21.4
Changes in other liabilities	(15.9)	19.3	23.3
Cash Flows from Operating Activities	1,497.8	912.7	803.8
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Additions to property, plant and equipment	(1,069.7)	(764.6)	(1,087)
Cash acquired from the merger with Great Plains Energy	1,154.2	0	0
Purchase of securities - trusts	(117.5)	(41)	(46.6)
Sale of securities - trusts	117.7	41.2	47
Investment in corporate-owned life insurance	(17.1)	(17)	(18.1)
Proceeds from investment in corporate-owned life insurance	6.8	4.2	114.7
Proceeds from settlement of interest rate swap	140.6	0	0
Other investing activities	(17.6)	(3.6)	(4.1)
Cash Flows from (used in) Investing Activities	197.4	(780.8)	(994.1)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Short term debt, net	(104)	(91.3)	116.2
Collateralized short-term borrowings, net	185	0	0
Proceeds from long-term debt	290.9	296.2	396.3
Proceeds from long-term debt of variable interest entity	0	0	162
Retirements of long-term debt	(395.8)	(125)	(50)
Retirements of Long Term Debt Of VIEs	(28.5)	(26.8)	(190.4)
Borrowings against cash surrender value of corporate-owned life insurance	56.5	55.1	57.8
Repayment of borrowings against cash surrender value of corporate-owned life insurance	(3.9)	(1)	(89.3)
Cash dividends paid	(475)	(223.1)	(204.3)
Repurchase of common stock	(1,042.3)	0	0
Other financing activities	(21.3)	(15.7)	(8.1)
Cash Flows from (used in) Financing Activities	(1,538.4)	(131.6)	190.2
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	156.8	0.3	(0.1)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
Beginning of period	3.5	3.2	3.3
End of period	160.3	3.5	3.2
Westar Energy Inc [Member]
Cash and cash equivalents	44.5	3.4
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income	349.1	336.5	361.2
Adjustments to reconcile income to net cash from operating activities:
Depreciation and amortization	390.9	371.7	338.5
Amortization of nuclear fuel	26	32.2	26.7
Amortization of deferred refueling outage	13.7	16.1	18.4
Amortization of deferred regulatory gain from sale leaseback	(5.5)	(5.5)	(5.5)
Amortization of corporate-owned life insurance	22.6	20.6	18
Non-cash compensation	19.9	8.8	9.3
Net deferred income taxes and credits	(2.2)	149.6	185.2
Allowance for equity funds used during construction	(2.9)	(2)	(11.6)
Payments for asset retirement obligations	(12)	(16)	(5.4)
Equity in earnings of equity method investees, net of income taxes	(4.6)	(6.7)	(6.5)
Other	(2.2)	(6)	(22)
Changes in working capital items:
Accounts receivable	207.9	(2.1)	(30.3)
Accounts receivable pledged as collateral	(185)	0	0
Fuel inventory and supplies	17.3	7.2	1.8
Prepaid expenses and other current assets	(134.2)	55.8	(18.3)
Accounts payable	(17.6)	10	(8.1)
Accrued taxes	(24.1)	9.2	(5.9)
Other current liabilities	88.3	(118)	(86.4)
Changes in other assets	42.7	32	21.4
Changes in other liabilities	(36.2)	19.3	23.3
Cash Flows from Operating Activities	751.9	912.7	803.8
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Additions to property, plant and equipment	(713.3)	(764.6)	(1,087)
Purchase of securities - trusts	(99.4)	(41)	(46.6)
Sale of securities - trusts	104.2	41.2	47
Investment in corporate-owned life insurance	(17.1)	(17)	(18.1)
Proceeds from investment in corporate-owned life insurance	6.8	4.2	114.7
Other investing activities	(8.6)	(3.6)	(4.1)
Cash Flows from (used in) Investing Activities	(727.4)	(780.8)	(994.1)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Short term debt, net	133.7	(91.3)	116.2
Collateralized short-term borrowings, net	185	0	0
Proceeds from long-term debt	121.9	296.2	396.3
Proceeds from long-term debt of variable interest entity	0	0	162
Retirements of long-term debt	(121.9)	(125)	(50)
Retirements of Long Term Debt Of VIEs	(28.5)	(26.8)	(190.4)
Borrowings against cash surrender value of corporate-owned life insurance	56.5	55.1	57.8
Repayment of borrowings against cash surrender value of corporate-owned life insurance	(3.9)	(1)	(89.3)
Cash dividends paid	(305.1)	(223.1)	(204.3)
Other financing activities	(21.2)	(15.7)	(8.1)
Cash Flows from (used in) Financing Activities	16.5	(131.6)	190.2
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	41	0.3	(0.1)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
Beginning of period	3.5	3.2	3.3
End of period	44.5	3.5	3.2
KCPL [Member]
Cash and cash equivalents	2.6	2.2
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income	162.9	179.8	225
Adjustments to reconcile income to net cash from operating activities:
Depreciation and amortization	281.3	266.3	247.5
Amortization of nuclear fuel	26.2	32.1	26.6
Amortization of deferred refueling outage	13.5	18.3	19
Net deferred income taxes and credits	48.6	82.5	92.4
Allowance for equity funds used during construction	(1.4)	(6)	(6.6)
Payments for asset retirement obligations	(13.1)	(25.5)	(15)
Other	3.9	7.5	8.8
Changes in working capital items:
Accounts receivable	36.5	13.8	(12.4)
Accounts receivable pledged as collateral	0	(20)	0
Fuel inventory and supplies	19.4	(5.2)	6.3
Prepaid expenses and other current assets	7.2	8.4	(73.2)
Accounts payable	(34.6)	11.7	(30.5)
Accrued taxes	16.1	9.1	67.9
Other current liabilities	10.4	(0.1)	10.4
Changes in other assets	42.9	31.7	66.5
Changes in other liabilities	37.9	6.5	(9.4)
Cash Flows from Operating Activities	657.7	610.9	623.3
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Additions to property, plant and equipment	(430.7)	(468.6)	(447.9)
Purchase of securities - trusts	(35.1)	(33.6)	(31.9)
Sale of securities - trusts	27.1	30.3	28.6
Other investing activities	4.8	0.9	(0.3)
Cash Flows from (used in) Investing Activities	(433.9)	(471)	(451.5)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Short term debt, net	8	34.6	(47.4)
Collateralized short-term borrowings, net	0	20	0
Proceeds from long-term debt	465.6	296.2	0
Retirements of long-term debt	(519.9)	(281)	0
Cash dividends paid	(180)	(212)	(122)
Other financing activities	2.9	0	(0.2)
Cash Flows from (used in) Financing Activities	(223.4)	(142.2)	(169.6)
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	0.4	(2.3)	2.2
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
Beginning of period	2.2	4.5	2.3
End of period	$ 2.6	$ 2.2	$ 4.5

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted cash	$ 0	$ 0.1	$ 0.1	$ 0.1
Westar Energy Inc [Member]
Restricted cash	$ 0	$ 0.1	$ 0.1	$ 0.1

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]	AOCI [Member]	Westar Energy Inc [Member]	Westar Energy Inc [Member]Common Stock [Member]	Westar Energy Inc [Member]Retained Earnings [Member]	Westar Energy Inc [Member]Noncontrolling Interest [Member]	KCPL [Member]	KCPL [Member]Common Stock [Member]	KCPL [Member]Retained Earnings [Member]	KCPL [Member]AOCI [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of adoption of ASU 2016-09	$ 3.3		$ 3.3			$ 3.3		$ 3.3
Beginning balance (in shares) at Dec. 31, 2015		141,353,426					141,353,426				1
Beginning balance at Dec. 31, 2015	3,671.9	$ 2,710.9	945.8	$ 15.2		3,671.9	$ 2,710.9	945.8	$ 15.2	$ 2,433.1	$ 1,563.1	$ 879.6	$ (9.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	361.2		346.6	14.6		361.2		346.6	14.6	225		225
Issuance of stock	2.4	$ 2.4				2.4	$ 2.4
Issuance of stock (in shares)		48,101					48,101
Issuance of stock for compensation and reinvested dividends (in shares)		389,626					389,626
Issuance of stock for compensation and reinvested dividends	9.7	$ 9.7				9.7	$ 9.7
Tax withholding related to stock compensation	(5)	(5)				(5)	(5)
Dividends declared on common stock	(217.1)		(217.1)			(217.1)		(217.1)		(122)		(122)
Stock compensation expense	9.3	$ 9.3				9.3	$ 9.3
Distributions to shareholders of noncontrolling interests	(2.5)			(2.5)		(2.5)			(2.5)
Derivative hedging activity, net of tax	0									5.4			5.4
Change in unrecognized pension expense, net of tax	0
Ending balance (in shares) at Dec. 31, 2016		141,791,153					141,791,153				1
Ending balance at Dec. 31, 2016	3,833.2	$ 2,727.3	1,078.6	27.3		3,833.2	$ 2,727.3	1,078.6	27.3	2,541.5	$ 1,563.1	982.6	(4.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of adoption of ASU 2016-09										(0.7)		(0.7)
Net income	336.5		323.9	12.6		336.5		323.9	12.6	179.8		179.8
Issuance of stock	0.6	$ 0.6				0.6	$ 0.6
Issuance of stock (in shares)		12,131					12,131
Issuance of stock for compensation and reinvested dividends (in shares)		290,991					290,991
Issuance of stock for compensation and reinvested dividends	5.1	$ 5.1				5.1	$ 5.1
Tax withholding related to stock compensation	(7)	(7)				(7)	(7)
Dividends declared on common stock	(229.2)		(229.2)			(229.2)		(229.2)		(212)		(212)
Stock compensation expense	8.8	$ 8.8				8.8	$ 8.8
Deconsolidation of noncontrolling interests	(81.9)			(81.9)		(81.9)			(81.9)
Distributions to shareholders of noncontrolling interests	(5.7)			(5.7)		(5.7)			(5.7)
Derivative hedging activity, net of tax	0									4.6			4.6
Change in unrecognized pension expense, net of tax	0
Ending balance (in shares) at Dec. 31, 2017		142,094,275					142,094,275				1
Ending balance at Dec. 31, 2017	3,860.4	$ 2,734.8	1,173.3	(47.7)		3,860.4	$ 2,734.8	1,173.3	(47.7)	2,513.2	$ 1,563.1	949.7	0.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	546		535.8	10.2		349.1		338.9	10.2	162.9		162.9
Issuance of stock to Great Plains Energy shareholders (in shares)		128,947,518
Issuance of stock to Great Plains Energy shareholders	6,979.9	$ 6,979.9
Issuance of restricted common stock (in shares)		122,505
Issuance of stock for compensation and reinvested dividends (in shares)		533,273					516,990
Issuance of stock for compensation and reinvested dividends	0.5	$ 0.5				0
Tax withholding related to stock compensation	(17.2)	(17.2)				(17.2)	$ (17.2)
Dividends declared on common stock	(362.1)		(362.1)			(251.6)		(251.6)		(180)		(180)
Dividend equivalents declared	(1)		(1)
Stock compensation expense	29.9	29.9				19.9	$ 19.9
Repurchase of common stock	(1,042.3)	$ (1,042.3)
Repurchase of common stock		(16,371,319)
Stock cancelled pursuant to Amended Merger Agreement (in shares)							(142,611,264)
Stock cancelled pursuant to Amended Merger Agreement						0
Derivative hedging activity, net of tax	(4)				$ (4)					3.7			3.7
Change in unrecognized pension expense, net of tax	1				1
Other	(0.4)	$ (0.4)				0.1	$ 0.1
Ending balance (in shares) at Dec. 31, 2018		255,326,252					1				1
Ending balance at Dec. 31, 2018	$ 9,990.7	$ 8,685.2	$ 1,346	$ (37.5)	$ (3)	$ 3,960.7	$ 2,737.6	$ 1,260.6	$ (37.5)	$ 2,499.8	$ 1,563.1	$ 932.6	$ 4.1

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Dividends declared on common stock (in dollars per share)	$ 1.735	$ 1.60	$ 1.52

Summary of Significant Accounti

Summary of Significant Accounting Policies Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Organization Evergy is a public utility holding company incorporated in 2017 and headquartered in Kansas City, Missouri. Evergy operates primarily through the following wholly-owned direct subsidiaries: • Westar Energy is an integrated, regulated electric utility that provides electricity to customers in the state of Kansas. Westar Energy has one active wholly-owned subsidiary with significant operations, Kansas Gas and Electric Company (KGE). • KCP&L is an integrated, regulated electric utility that provides electricity to customers in the states of Missouri and Kansas. • KCP&L Greater Missouri Operations Company (GMO) is an integrated, regulated electric utility that provides electricity to customers in the state of Missouri. • GPE Transmission Holding Company, LLC (GPETHC) owns 13.5% of Transource Energy, LLC (Transource) with the remaining 86.5% owned by AEP Transmission Holding Company, LLC, a subsidiary of American Electric Power Company, Inc. (AEP). Transource is focused on the development of competitive electric transmission projects. GPETHC accounts for its investment in Transource under the equity method. Westar Energy also owns a 50% interest in Prairie Wind Transmission, LLC (Prairie Wind), which is a joint venture between Westar Energy and affiliates of AEP and Berkshire Hathaway Energy Company. Prairie Wind owns a 108-mile, 345 kV double-circuit transmission line that provides transmission service in the Southwest Power Pool, Inc. (SPP). Westar Energy accounts for its investment in Prairie Wind under the equity method. Westar Energy and KGE conduct business in their respective service territories using the name Westar Energy. KCP&L and GMO conduct business in their respective service territories using the name KCP&L. Collectively, the Evergy Companies have approximately 14,500 MWs of owned generating capacity and renewable purchased power agreements and engage in the generation, transmission, distribution and sale of electricity to approximately 1.6 million customers in the states of Kansas and Missouri. Evergy was incorporated in 2017 as Monarch Energy Holding, Inc. (Monarch Energy), a wholly-owned subsidiary of Great Plains Energy Incorporated (Great Plains Energy). Prior to the closing of the merger transactions, Monarch Energy changed its name to Evergy and did not conduct any business activities other than those required for its formation and matters contemplated by the Amended and Restated Agreement and Plan of Merger, dated as of July 9, 2017, by and among Great Plains Energy, Westar Energy, Monarch Energy and King Energy, Inc. (King Energy), a wholly-owned subsidiary of Monarch Energy (Amended Merger Agreement). On June 4, 2018, in accordance with the Amended Merger Agreement, Great Plains Energy merged into Evergy, with Evergy surviving the merger and King Energy merged into Westar Energy, with Westar Energy surviving the merger. These merger transactions resulted in Evergy becoming the parent entity of Westar Energy and the direct subsidiaries of Great Plains Energy, including KCP&L and GMO. See Note 2 for additional information regarding the merger. Principles of Consolidation Westar Energy was determined to be the accounting acquirer in the merger and thus, the predecessor of Evergy. Therefore, Evergy's consolidated financial statements reflect the results of operations of Westar Energy for 2017 and 2016 and the financial position of Westar Energy as of December 31, 2017. Evergy had separate operations for the period beginning with the quarter ended June 30, 2018, and references to amounts for periods after the closing of the merger relate to Evergy. The results of Great Plains Energy's direct subsidiaries have been included in Evergy's results of operations from the date of the closing of the merger and thereafter. Westar Energy and KCP&L continue to be Securities and Exchange Commission (SEC) registrants. KCP&L has elected not to apply "push-down accounting" related to the merger, whereby the adjustments of assets and liabilities to fair value and the resulting goodwill would be recorded on the financial statements of the acquired subsidiary. These adjustments for KCP&L, as well as those related to the acquired assets and liabilities of Great Plains Energy and its other direct subsidiaries, are only reflected on Evergy's consolidated financial statements. Each of Evergy's, Westar Energy's and KCP&L's consolidated financial statements includes the accounts of their subsidiaries and variable interest entities (VIEs) of which they are the primary beneficiary. Undivided interests in jointly-owned generation facilities are included on a proportionate basis. Intercompany transactions have been eliminated. The Evergy Companies assess financial performance and allocate resources on a consolidated basis (i.e., operate in one segment). Certain changes in classification and corresponding reclassification of prior period data were made in Evergy's, Westar Energy's and KCP&L's consolidated balance sheets, statements of income and comprehensive income and statements of cash flows for comparative purposes. Evergy reflects the classifications of Westar Energy as the accounting acquirer in the merger. These reclassifications did not affect Evergy's, Westar Energy's or KCP&L's net income or Evergy's, Westar Energy's or KCP&L's cash flows from operations, investing or financing. Most significantly for Westar Energy's consolidated balance sheets as of December 31, 2017, was the reclassification of $50.2 million from accrued employee benefits (currently reported as pension and post-retirement liability) to other long-term liabilities. Most significantly for KCP&L's consolidated balance sheets, current regulatory assets and liabilities have been presented separately from the non-current portions in each respective consolidated balance sheet where recovery or refund is expected within the next 12 months. The table below summarizes KCP&L's reclassifications related to operating and investing activities for its consolidated statement of cash flows for 2017 and 2016. 2017 2016 As Previously Filed As Recast As Previously Filed As Recast CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES: (in millions) Adjustments to reconcile income to net cash from operating activities: Amortization of other $ 30.2 $ — $ 33.9 $ — Amortization of deferred refueling outage — 18.3 — 19.0 Deferred income taxes, net 83.5 — 93.4 — Investment tax credit amortization (1.0 ) — (1.0 ) — Net deferred income taxes and credits — 82.5 — 92.4 Payments for asset retirement obligations (25.5 ) (25.5 ) — (15.0 ) Other/Solar rebates paid (a) (9.0 ) 7.5 1.4 8.8 Changes in working capital items: Fuel inventory and supplies — (5.2 ) — 6.3 Fuel inventories (a) 1.9 — 10.6 — Materials and supplies (a) (7.1 ) — (4.3 ) — Prepaid expenses and other current assets — 8.4 — (73.2 ) Other current liabilities — (0.1 ) — 10.4 Changes in other assets — 31.7 — 66.5 Changes in other liabilities — 6.5 — (9.4 ) Deferred refueling outage costs (a) 15.5 — (3.1 ) — Pension and post-retirement benefit obligations (a) 27.3 — 28.6 — Fuel recovery mechanisms (a) 8.3 — (53.7 ) — Total reclassifications $ 124.1 $ 124.1 $ 105.8 $ 105.8 CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES: Additions to property, plant and equipment $ — $ (468.6 ) $ — $ (447.9 ) Utility capital expenditures (437.7 ) — (418.8 ) — Allowance for borrowed funds used during construction (6.1 ) — (5.6 ) — Other investing activities (23.9 ) 0.9 (23.8 ) (0.3 ) Total reclassifications $ (467.7 ) $ (467.7 ) $ (448.2 ) $ (448.2 ) (a) Previously reported within Note 3 to the consolidated financial statements of the Great Plains Energy and KCP&L combined 2017 and 2016 Annual Reports on Form 10-K. Use of Estimates The process of preparing financial statements in conformity with generally accepted accounting principles (GAAP) requires the use of estimates and assumptions that affect the reported amounts of certain types of assets, liabilities, revenues and expenses. Such estimates primarily relate to unsettled transactions and events as of the date of the financial statements. Accordingly, upon settlement, actual results may differ from estimated amounts. Cash and Cash Equivalents Cash equivalents consist of highly liquid investments with original maturities of three months or less at acquisition. Fuel Inventory and Supplies The Evergy Companies record fuel inventory and supplies at average cost. The following table separately states the balances for fuel inventory and supplies. December 31 2018 2017 Evergy (millions) Fuel inventory $ 168.9 $ 94.1 Supplies 342.1 199.5 Fuel inventory and supplies $ 511.0 $ 293.6 Westar Energy Fuel inventory $ 87.8 $ 94.1 Supplies 189.0 199.5 Fuel inventory and supplies $ 276.8 $ 293.6 KCP&L (a) Fuel inventory $ 57.8 $ 71.0 Supplies 119.8 126.0 Fuel inventory and supplies $ 177.6 $ 197.0 (a) KCP&L amounts are not included in consolidated Evergy at December 31, 2017. Property, Plant and Equipment The Evergy Companies record the value of property, plant and equipment, including that of variable interest entities (VIEs), at cost. For plant, cost includes contracted services, direct labor and materials, indirect charges for engineering and supervision and an allowance for funds used during construction (AFUDC). AFUDC represents the allowed cost of capital used to finance utility construction activity. AFUDC equity funds are included as a non-cash item in other income and AFUDC borrowed funds are a reduction of interest expense. AFUDC is computed by applying a composite rate to qualified construction work in progress. The rates used to compute gross AFUDC are compounded semi-annually. The amounts of the Evergy Companies' AFUDC for borrowed and equity funds are detailed in the following table. 2018 2017 2016 Evergy (millions) AFUDC borrowed funds $ 10.4 $ 5.6 $ 10.0 AFUDC equity funds 3.1 2.0 11.6 Total $ 13.5 $ 7.6 $ 21.6 Westar Energy AFUDC borrowed funds $ 6.6 $ 5.6 $ 10.0 AFUDC equity funds 2.9 2.0 11.6 Total $ 9.5 $ 7.6 $ 21.6 KCP&L (a) AFUDC borrowed funds $ 4.9 $ 6.1 $ 5.6 AFUDC equity funds 1.4 6.0 6.6 Total $ 6.3 $ 12.1 $ 12.2 (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018 through December 31, 2018. The average rates used in the calculation of AFUDC are detailed in the following table. 2018 2017 2016 Westar Energy 3.3% 2.3% 4.2% KCP&L 3.9% 4.9% 5.7% GMO 2.9% 1.9% 1.6% When property units are retired or otherwise disposed, the original cost net of salvage is charged to accumulated depreciation. Repair of property and replacement of items not considered to be units of property are expensed as incurred, except for planned refueling and maintenance outages at Wolf Creek Generating Station (Wolf Creek). As authorized by regulators, the expense is deferred and amortized ratably over the period between planned outages incremental maintenance cost incurred for such outages. Depreciation and Amortization Depreciation and amortization of utility plant other than nuclear fuel is computed using the straight-line method over the estimated lives of depreciable property based on rates approved by state regulatory authorities. Annual depreciation rates average approximately 3% . Nuclear fuel is amortized to fuel expense based on the quantity of heat produced during the generation of electricity. See Note 7 for more details. The depreciable lives of Evergy's, Westar Energy's and KCP&L's property, plant and equipment are detailed in the following table. Evergy Westar Energy KCP&L (years) Generating facilities 8 to 87 8 to 87 20 to 60 Transmission facilities 15 to 94 36 to 94 15 to 70 Distribution facilities 8 to 73 19 to 73 8 to 55 Other 5 to 84 7 to 84 5 to 50 Plant to be Retired, Net When the Evergy Companies retire utility plant, the original cost, net of salvage, is charged to accumulated depreciation. However, when it becomes probable an asset will be retired significantly in advance of its original expected useful life and in the near term, the cost of the asset and related accumulated depreciation is recognized as a separate asset and a probable abandonment. If the asset is still in service, the net amount is classified as plant to be retired, net on the consolidated balance sheets. If the asset is no longer in service, the net amount is classified as a regulatory asset on the consolidated balance sheets. The Evergy Companies must also assess the probability of full recovery of the remaining net book value of the abandonment. The net book value that may be retained as an asset on the balance sheet for the abandonment is dependent upon amounts that may be recovered through regulated rates, including any return. An impairment charge, if any, would equal the difference between the remaining net book value of the asset and the present value of the future revenues expected from the asset. In June 2017, GMO announced the expected retirement of certain older generating units, including GMO's Sibley No. 3 Unit, over the next several years. GMO determined that Sibley No. 3 Unit met the criteria to be considered probable of abandonment. GMO retired Sibley Station, including the No. 3 Unit, in November 2018. As of December 31, 2018 , Evergy has classified the remaining Sibley No. 3 Unit net book value of $159.9 million as retired generation facilities within regulatory assets on its consolidated balance sheet. Evergy is currently allowed a full recovery of and a full return on Sibley No. 3 Unit in rates and has concluded that no impairment is required as of December 31, 2018 . Nuclear Plant Decommissioning Costs Nuclear plant decommissioning cost estimates are based on either the immediate dismantlement method or the deferred dismantling method as determined by the KCC and MPSC and include the costs of decontamination, dismantlement and site restoration. Based on these cost estimates, Westar Energy and KCP&L contribute to a tax-qualified trust fund to be used to decommission Wolf Creek. Related liabilities for decommissioning are included on Evergy's, Westar Energy's and KCP&L's consolidated balance sheets in Asset Retirement Obligations (AROs). As a result of the authorized regulatory treatment and related regulatory accounting, differences between the decommissioning trust fund asset and the related ARO are recorded as a regulatory asset or liability. See Note 6 for discussion of AROs including those associated with nuclear plant decommissioning costs. Regulatory Accounting Accounting standards are applied that recognize the economic effects of rate regulation. Accordingly, regulatory assets and liabilities have been recorded when required by a regulatory order or based on regulatory precedent. See Note 5 for additional information concerning regulatory matters. Cash Surrender Value of Life Insurance Amounts related to corporate-owned life insurance (COLI) are recorded on the consolidated balance sheets in other long-terms assets and are detailed in the following table for Evergy. Substantially all of Evergy's COLI-related balances relate to Westar Energy's COLI activity. December 31 2018 2017 Evergy (millions) Cash surrender value of policies $ 1,441.7 $ 1,320.7 Borrowings against policies (1,306.9 ) (1,189.2 ) Corporate-owned life insurance, net $ 134.8 $ 131.5 Increases in cash surrender value and death benefits are recorded in other income in the Evergy Companies' consolidated statements of income and comprehensive income. Interest expense incurred on policy loans is offset against the policy income. Income from death benefits is highly variable from period to period. Fair Value of Financial Instruments The following methods and assumptions were used to estimate the fair value of the following financial instruments for which it was practicable to estimate that value. Nuclear decommissioning trust fund - The Evergy Companies' nuclear decommissioning trust fund assets are recorded at fair value based on quoted market prices of the investments held by the fund and/or valuation models. Pension plans - For financial reporting purposes, the market value of plan assets is the fair value. Revenue Recognition The Evergy Companies recognize revenue on the sale of electricity to customers over time as the service is provided in the amount they have the right to invoice. Revenues recorded include electric services provided but not yet billed by the Evergy Companies. Unbilled revenues are recorded for kWh usage in the period following the customers' billing cycle to the end of the month. This estimate is based on net system kWh usage less actual billed kWhs. The Evergy Companies' estimated unbilled kWhs are allocated and priced by regulatory jurisdiction across the rate classes based on actual billing rates. The Evergy Companies' unbilled revenue estimate is affected by factors including fluctuations in energy demand, weather, line losses and changes in the composition of customer classes. See Note 4 for the balance of unbilled receivables for each of Evergy, Westar Energy and KCP&L as of December 31, 2018 and 2017. The Evergy Companies also collect sales taxes and franchise fees from customers concurrent with revenue-producing activities that are levied by state and local governments. These items are excluded from revenue, and thus are not reflected on the consolidated statements of income and comprehensive income for Evergy, Westar Energy and KCP&L. See Note 3 for additional details regarding revenue recognition from sales of electricity by the Evergy Companies. Allowance for Doubtful Accounts The Evergy Companies determine their allowance for doubtful accounts based on the age of their receivables. Receivables are charged off when they are deemed uncollectible, which is based on a number of factors including specific facts surrounding an account and management's judgment. Property Gains and Losses Net gains and losses from the sale of assets and businesses and from asset impairments are recorded in operating expenses. Asset Impairments Long-lived assets and finite-lived intangible assets subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If the sum of the undiscounted expected future cash flows from an asset to be held and used is less than the carrying value of the asset, an asset impairment must be recognized in the financial statements. The amount of impairment recognized is the excess of the carrying value of the asset over its fair value. Goodwill and indefinite lived intangible assets are tested for impairment annually and when an event occurs indicating the possibility that an impairment exists. The annual test must be performed at the same time each year. Evergy's first impairment test for the $2,338.9 million of goodwill from the Great Plains Energy and Westar Energy merger will be conducted on May 1, 2019. The goodwill impairment test consists of comparing the fair value of a reporting unit to its carrying amount, including goodwill, to identify potential impairment. In the event that the carrying amount exceeds the fair value of the reporting unit, an impairment loss is recognized for the difference between the carrying amount of the reporting unit and its fair value. Income Taxes Income taxes are accounted for using the asset/liability approach. Deferred tax assets and liabilities are determined based on the temporary differences between the financial reporting and tax bases of assets and liabilities, applying enacted statutory tax rates in effect for the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion of the deferred tax assets will not be realized. The Evergy Companies recognize tax benefits based on a "more-likely-than-not" recognition threshold. In addition, the Evergy Companies recognize interest accrued related to unrecognized tax benefits in interest expense and penalties in operating expenses. Evergy files a consolidated federal income tax return as well as unitary and combined income tax returns in several state jurisdictions with Kansas and Missouri being the most significant. Income taxes for consolidated or combined subsidiaries are allocated to the subsidiaries based on separate company computations of income or loss. Westar Energy's and KCP&L's income tax provisions include taxes allocated based on their separate company's income or loss. The Evergy Companies have established a net regulatory liability for future refunds to be made to customers for the over-collection of income taxes in rates. Tax credits are recognized in the year generated except for certain Westar Energy, KCP&L and GMO investment tax credits that have been deferred and amortized over the remaining service lives of the related properties. Other Income (Expense), Net The table below shows the detail of other expense for each of the Evergy Companies. 2018 2017 2016 Evergy (millions) Non-service cost component of net benefit cost $ (47.8 ) $ (20.0 ) $ (20.6 ) Other (30.9 ) (19.1 ) (18.0 ) Other expense $ (78.7 ) $ (39.1 ) $ (38.6 ) Westar Energy Non-service cost component of net benefit cost $ (23.5 ) $ (20.0 ) $ (20.6 ) Other (23.3 ) (19.1 ) (18.0 ) Other expense $ (46.8 ) $ (39.1 ) $ (38.6 ) KCP&L (a) Non-service cost component of net benefit cost $ (25.9 ) $ (42.7 ) $ (37.2 ) Other (5.0 ) (8.1 ) (7.6 ) Other expense $ (30.9 ) $ (50.8 ) $ (44.8 ) (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018 through December 31, 2018. Earnings Per Share To compute basic earnings per share (EPS), Evergy divides net income attributable to Evergy, Inc. by the weighted average number of common shares outstanding. Diluted EPS includes the effect of issuable common shares resulting from restricted share units (RSUs), performance shares and restricted stock. Evergy computes the dilutive effects of potential issuances of common shares using the treasury stock method. The following table reconciles Evergy's basic and diluted EPS. 2018 2017 2016 Income (millions, except per share amounts) Net income $ 546.0 $ 336.5 $ 361.2 Less: Net income attributable to noncontrolling interests 10.2 12.6 14.6 Net income attributable to Evergy, Inc. $ 535.8 $ 323.9 $ 346.6 Common Shares Outstanding Weighted average number of common shares outstanding - basic 213.9 142.5 142.1 Add: effect of dilutive securities 0.2 0.1 0.4 Diluted average number of common shares outstanding 214.1 142.6 142.5 Basic and Diluted EPS $ 2.50 $ 2.27 $ 2.43 There were no anti-dilutive securities excluded from the computation of diluted EPS for 2018, 2017 and 2016. Supplemental Cash Flow Information Year Ended December 31 2018 2017 2016 Evergy (millions) Cash paid for (received from): Interest on financing activities, net of amount capitalized $ 255.9 $ 153.9 $ 139.0 Interest on financing activities of VIEs 2.3 3.1 5.8 Income taxes, net of refunds (0.9 ) (12.7 ) 13.1 Non-cash investing transactions: Property, plant and equipment additions (reductions) (7.8 ) 158.8 151.5 Deconsolidation of property, plant and equipment of VIE — (72.9 ) — Non-cash financing transactions: Issuance of stock for compensation and reinvested dividends 0.5 5.1 9.7 Deconsolidation of VIE — (83.1 ) — Assets acquired through capital leases 1.2 4.8 2.7 Year Ended December 31 2018 2017 2016 Westar Energy (millions) Cash paid for (received from): Interest on financing activities, net of amount capitalized $ 155.3 $ 153.9 $ 139.0 Interest on financing activities of VIEs 2.3 3.1 5.8 Income taxes, net of refunds 37.5 (12.7 ) 13.1 Non-cash investing transactions: Property, plant and equipment additions (reductions) (32.5 ) 158.8 151.5 Deconsolidation of property, plant and equipment of VIE — (72.9 ) — Non-cash financing transactions: Issuance of stock for compensation and reinvested dividends — 5.1 9.7 Deconsolidation of VIE — (83.1 ) — Assets acquired through capital leases 1.2 4.8 2.7 Year Ended December 31 2018 2017 2016 KCP&L (a) (millions) Cash paid for (received from): Interest on financing activities, net of amount capitalized $ 129.4 $ 128.0 $ 127.0 Income taxes, net of refunds 31.2 38.8 (37.3 ) Non-cash investing transactions: Property, plant and equipment additions 19.2 36.6 75.4 (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018. See Note 2 for the non-cash information related to the merger transaction, including the fair value of Great Plains Energy's assets acquired and liabilities assumed and the issuance of Evergy common stock. Dividends Declared In February 2019 , Evergy's Board of Directors (Evergy Board) declared a quarterly dividend of $0.475 per share on Evergy's common stock. The common dividend is payable March 20, 2019 , to shareholders of record as of February 27, 2019 . In February 2019 , Westar Energy's Board of Directors declared a cash dividend payable to Evergy of $110.0 million , payable on March 19, 2019 . New Accounting Standards Intangibles - Internal-Use Software In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-15, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , which aligns the requirements for recording implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. An entity in a hosting arrangement that is a service contract will need to determine which project stage (that is, preliminary project stage, application development stage or post-implementation stage) an implementation activity relates. Costs for implementation activities in the application development stage are recorded as a prepaid asset depending on the nature of the costs, while costs incurred during the preliminary project and post-implementation stages are expensed as the activities are incurred. Costs that are recorded to a prepaid asset are to be expensed over the term of the hosting arrangement. The new guidance is effective for annual periods beginning after December 15, 2019, and interim periods within those fiscal years. The new guidance can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. Early adoption is permitted. The Evergy Companies early adopted ASU No. 2018-15 prospectively as of January 1, 2019. The adoption of ASU No. 2018-15 did not have a material impact on the Evergy Companies. Compensation - Retirement Benefits In March 2017, the FASB issued ASU No. 2017-07, Compensation-Retirement Benefits , which requires an employer to disaggregate the service cost component from the other components of net benefit cost. The service cost component is to be reported in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The non-service cost components are to be reported separately from service costs and outside of a subtotal of income from operations. The amendments in this update allow only the service cost component to be eligible for capitalization as part of utility plant. The non-service cost components that are no longer eligible for capitalization as part of utility plant will be recorded as a regulatory asset. The new guidance is to be applied retrospectively for the presentation of service cost and non-service cost components in the income statement and prospectively for the capitalization of the service cost component and is effective for interim and annual periods beginning after December 15, 2017. The Evergy Companies adopted ASU No. 2017-07 on January 1, 2018, and accordingly have retrospectively adjusted prior periods. The Evergy Companies utilized the practical expedient that allows for the use of amounts disclosed in Note 9 for applying the retrospective presentation to the 2017 and 2016 consolidated statements of income and comprehensive income. The following table reflects the retrospective adjustments in the line items of Evergy's, Westar Energy's and KCP&L's consolidated statements of income and comprehensive income associated with the adoption of ASU No. 2017 -07. 2017 2016 As Previously Reported (b) Effect of Change As Reported As Previously Reported (b) Effect of Change As Reported Evergy (millions) Operating and maintenance expense $ 583.5 $ (20.0 ) $ 563.5 $ 607.8 $ (20.6 ) $ 587.2 Total operating expenses 1,912.2 (20.0 ) 1,892.2 1,880.3 (20.6 ) 1,859.7 Income from operations 658.8 20.0 678.8 681.8 20.6 702.4 Other expense (19.1 ) (20.0 ) (39.1 ) (18.0 ) (20.6 ) (38.6 ) Total other income (expense), net (6.8 ) (20.0 ) (26.8 ) 19.1 (20.6 ) (1.5 ) Westar Energy Operating and maintenance expense $ 583.5 $ (20.0 ) $ 563.5 $ 607.8 $ (20.6 ) $ 587.2 Total operating expenses 1,912.2 (20.0 ) 1,892.2 1,880.3 (20.6 ) 1,859.7 Income from operations 658.8 20.0 678.8 681.8 20.6 702.4 Other expense (19.1 ) (20.0 ) (39.1 ) (18.0 ) (20.6 ) (38.6 ) Total other income (expense), net (6.8 ) (20.0 ) (26.8 ) 19.1 (20.6 ) (1.5 ) KCP&L (a) Operating and maintenance expense $ 517.5 $ (42.7 ) $ 474.8 $ 539.2 $ (37.2 ) $ 502.0 Total operating expenses 1,447.0 (42.7 ) 1,404.3 1,393.3 (37.2 ) 1,356.1 Income from operations 443.7 42.7 486.4 482.1 37.2 519.3 Other expense (8.1 ) (42.7 ) (50.8 ) (7.6 ) (37.2 ) (44.8 ) Total other income (expense), net 3.1 (42.7 ) (39.6 ) 4.2 (37.2 ) (33.0 ) (a) KCP&L amounts are not included in consolidated Evergy for 2017 and 2016. (b) Certain Evergy, Westar Energy and KCP&L as previously reported amounts have been adjusted to reflect reclassification adjustments made for comparative purposes as discussed further in Principles of Consolidation above and that have no impact on net income. Statement of Cash Flows In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments , which clarifies how certain cash receipts and cash payments are presented and classified in the statement of cash flows. Among other clarifications, the guidance requires that cash proceeds received from the settlement of COLI policies be classified as cash inflows from investing activities and that cash payments for premiums on COLI policies may be classified as cash outflows for investing activities, operating activities or a combination of both. Retrospective application is required. The Evergy Companies adopted the guidance effective January 1, 2018, which resulted in retrospective reclassification of cash proceeds of $2.8 million and $22.1 million from the settlement of COLI policies from cash inflows from operating activities to cash inflows from investing activities for 2017 and 2016 , respectively, for Evergy and Westar Energy. In addition, cash payments of $3.1 million and $3.4 million for premiums on COLI policies were reclassified from cash outflows used in operating activities to cash outflows used in investing activities for the same periods, respectively, for Evergy and Westar Energy. The adoption of ASU No. 2016-15 did not have a material impact on KCP&L. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows: Restricted Cash , which requires that the statement of cash flows explains the change for the period of restricted cash and restricted cash equivalents along with cash and cash equivalents. The guidance requires a retrospective transition method and is effective for fiscal years beginning after December 15, 2017. The Evergy Companies adopted the guidance effective January 1, 2018. As a result, Evergy and Westar Energy adjusted amounts previously reported for cash and cash equivalents to include restricted cash, which resulted in an increase to beginning and ending cash, cash equivalents and restricted cash of $0.1 million for 2017 and 2016 . The adoption of ASU No. 2016-18 did not have a material impact on KCP&L. Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which requires an entity that is a lessee to record a right-of-use asset and a lease liability for lease payments on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. Lessor accounting remains largely unchanged. In January 2018, the FASB is

Merger of Great Plains Energy a

Merger of Great Plains Energy and Westar Energy	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Merger of Great Plains Energy and Westar Energy	2 . MERGER OF GREAT PLAINS ENERGY AND WESTAR ENERGY Description of Merger Transaction On June 4, 2018, Evergy completed the mergers contemplated by the Amended Merger Agreement. As a result of the mergers, Great Plains Energy merged into Evergy, with Evergy surviving the merger and King Energy merged into Westar Energy, with Westar Energy surviving the merger. Following the completion of these mergers, Westar Energy and the direct subsidiaries of Great Plains Energy, including KCP&L and GMO, became wholly-owned subsidiaries of Evergy. The merger was structured as a merger of equals in a tax-free exchange of shares that involved no premium paid or received with respect to either Great Plains Energy or Westar Energy. As a result of the closing of the merger transaction, each outstanding share of Great Plains Energy common stock was converted into 0.5981 shares of Evergy common stock and each outstanding share of Westar Energy common stock was converted into 1 share of Evergy common stock. As provided in the Amended Merger Agreement, substantially all of Westar Energy's outstanding equity compensation awards vested and were converted into a right to receive Evergy common stock and all of Great Plains Energy's outstanding equity compensation awards were converted into equivalent Evergy awards subject to the same terms and conditions at the Great Plains Energy merger exchange ratio of 0.5981 . Merger Related Regulatory Matters KCC In May 2018, the State Corporation Commission of the State of Kansas (KCC) approved Great Plains Energy's, KCP&L's and Westar Energy's joint application for approval of the merger, including a settlement agreement that had been reached between Great Plains Energy, KCP&L, Westar Energy, KCC staff and certain other intervenors in the case. Through the joint application and settlement agreement, Great Plains Energy, KCP&L and Westar Energy agreed to the conditions and obligations listed below, in addition to other organizational, financing, customer service and civic responsibility commitments. • Provide a total of $30.6 million of one-time bill credits to Kansas electric retail customers as soon as practicable following the close of the merger and the completion of Westar Energy's and KCP&L's current rate cases in Kansas. Of this total, $23.1 million of the credits relate to Westar Energy customers and the remaining $7.5 million of credits relate to KCP&L Kansas customers. • Provide a total of approximately $46 million in additional bill credits consisting of $11.5 million in annual bill credits to Kansas electric retail customers from 2019 through 2022. Of the annual amount, $8.7 million of the credits relate to Westar Energy customers and the remaining $2.8 million of credits relate to KCP&L Kansas customers. • Provide for the inclusion of a total of $30.0 million of merger-related savings in Westar Energy's and KCP&L's current rate cases in Kansas. Of this total, $22.5 million of the savings are attributable to Westar Energy with the remaining $7.5 million of savings attributable to KCP&L's Kansas jurisdiction. • A five -year base rate moratorium for Westar Energy and KCP&L in Kansas that commenced following the conclusion of KCP&L's current Kansas rate case in December 2018. The moratorium is subject to certain conditions and does not include Westar Energy's or KCP&L's fuel recovery mechanisms and certain other cost recovery mechanisms in Kansas. • Require both Westar Energy and KCP&L to file rate cases in Kansas in a fashion that would allow for updated electric utility rates to become effective upon the end of the five -year rate moratorium in December 2023. • Participate in an Earnings Review and Sharing Plan for the years 2019 through 2022, which may result in Westar Energy and/or KCP&L being subject to refunding 50% of earned return on equity in excess of authorized return on equity to their Kansas customers. • Maintain charitable contributions and community involvement in the Kansas service territories of Westar Energy and KCP&L at levels equal to or greater than their respective 2015 levels for 5 years following the closing of the merger. • Commit that Westar Energy's and KCP&L's retail electric base rates will not increase as a result of the merger. • Allow Westar Energy and KCP&L to recover a total of $30.9 million of merger transition costs consisting of $23.2 million for Westar Energy and $7.7 million for KCP&L's Kansas jurisdiction. Westar Energy and KCP&L have recorded these amounts as regulatory assets and they are being recovered over a ten -year period. MPSC In May 2018, the Public Service Commission of the State of Missouri (MPSC) approved Great Plains Energy's, KCP&L's, GMO's and Westar Energy's joint application for approval of the merger, including two stipulations and agreements between these companies, MPSC staff and certain other intervenors in the case. Through the joint application and stipulations and agreements, Great Plains Energy, KCP&L, GMO and Westar Energy agreed to the conditions and obligations listed below, in addition to other organizational, financing, customer service and civic responsibility commitments. • Provide a total of $29.1 million of one-time bill credits to Missouri electric retail customers within 120 days following the close of the merger. Of this total, $14.9 million of the credits relate to KCP&L Missouri customers and the remaining $14.2 million of credits relate to GMO customers. • Commit that KCP&L's and GMO's retail electric base rates will not increase as a result of the merger. • Maintain charitable contributions and community involvement in the Missouri service territories of KCP&L and GMO at levels equal to or greater than their respective 2015 levels for 5 years following the closing of the merger. • Provide a total of $3.0 million of support over 10 years to community agencies to promote low-income weatherization efforts. • Support the recovery of a total of $16.9 million of merger transition costs in KCP&L's and GMO's 2018 rate cases, consisting of $9.7 million for KCP&L's Missouri jurisdiction and $7.2 million for GMO. KCP&L and GMO recorded these amounts as regulatory assets and they will be recovered over a ten -year period. Accounting Charges and Deferrals Related to the Merger The following pre-tax reductions of revenue, expenses and deferral were recognized following the consummation of the merger and are included in the Evergy Companies' consolidated statements of income and comprehensive income for 2018. Description Income Statement Line Item Expected Payment Period Evergy Westar Energy KCP&L (millions) One-time bill credits Operating revenues 2018 - 2019 $ (59.7 ) $ (23.1 ) $ (22.4 ) Annual bill credits Operating revenues 2019 - 2022 (10.5 ) (7.9 ) (2.6 ) Total impact to operating revenues $ (70.2 ) $ (31.0 ) $ (25.0 ) Charitable contributions and community support Operating and maintenance 2018 - 2027 $ 24.7 $ — $ — Voluntary severance and accelerated equity compensation Operating and maintenance 2018 - 2019 47.9 44.2 2.6 Other transaction and transition costs Operating and maintenance 2018 51.0 21.5 2.1 Reallocation and deferral of merger transition costs Operating and maintenance n/a (47.8 ) (13.8 ) (23.2 ) Total impact to operating and maintenance expense $ 75.8 $ 51.9 $ (18.5 ) Total $ (146.0 ) $ (82.9 ) $ (6.5 ) Reductions of revenue related to customer bill credits and expenses related to charitable contributions and community support were incurred as a result of conditions in the MPSC and KCC merger orders and were recorded as liabilities in the amounts presented above following the consummation of the merger. Reductions of revenue for annual bill credits of $11.5 million for Westar Energy's and KCP&L's Kansas electric retail customers are recognized ratably in the twelve month period preceding their payment. Voluntary severance and accelerated equity compensation represent costs related to payments for voluntary severance and change in control plans, as well as the recording of unrecognized equity compensation costs and the incremental fair value associated with the vesting of outstanding Westar Energy equity compensation awards. Other transaction and transition costs include merger success fees and fees for other outside services incurred. Reallocation and deferral of merger transition costs represents the net reallocation of incurred merger transition costs between Evergy, Westar Energy, KCP&L and GMO and the subsequent deferral of these transition costs to a regulatory asset for future recovery in accordance with the KCC and MPSC merger orders. Purchase Price Based on an evaluation of the provisions of ASC 805, Business Combinations , Westar Energy was determined to be the accounting acquirer in the merger. Pursuant to the Amended Merger Agreement, Great Plains Energy's common stock shares were exchanged for Evergy common stock shares at the fixed exchange rate of 0.5981 . The total consideration transferred in the merger is based on the closing stock price of Westar Energy on June 4, 2018 and is calculated as follows. (millions, except share amounts) Great Plains Energy common stock shares outstanding as of June 4, 2018 215,800,074 Great Plains Energy restricted stock awards outstanding as of June 4, 2018 (204,825 ) Great Plains Energy shares to be converted to Evergy shares 215,595,249 Exchange ratio 0.5981 Evergy common stock shares issued to Great Plains Energy shareholders 128,947,518 Closing price of Westar Energy common stock as of June 4, 2018 $ 54.00 Fair value of Evergy shares issued to Great Plains Energy shareholders $ 6,963.2 Fair value of Great Plains Energy's equity compensation awards 12.5 Total purchase price $ 6,975.7 Great Plains Energy's equity compensation awards, including performance shares and restricted stock, were replaced by equivalent Evergy equity compensation awards subject to substantially the same terms and conditions upon the closing of the merger. In accordance with the accounting guidance in ASC 805, a portion of the fair value of these awards is attributable to the purchase price as it represents consideration transferred in the merger. Purchase Price Allocation The fair value of Great Plains Energy's assets acquired and liabilities assumed as of June 4, 2018 was determined based on significant estimates and assumptions that are judgmental in nature. Third-party valuation specialists were engaged to assist in the valuation of these assets and liabilities. The fair values of Great Plains Energy's assets acquired and liabilities assumed utilized for the purchase price allocation are preliminary to the extent that additional information is obtained about facts and circumstances that existed as of the acquisition date. The significant assets and liabilities for which preliminary valuation amounts are reflected as of the filing of this combined Form 10-K include the fair value of acquired long-term debt, asset retirement obligations, pension and post-retirement plans, accumulated deferred income tax liabilities and certain other long-term assets and liabilities. The majority of Great Plains Energy's operations are subject to the rate-setting authority of the MPSC, KCC and The Federal Energy Regulatory Commission (FERC) and are accounted for pursuant to GAAP, including the accounting guidance for regulated operations. The rate-setting and cost recovery provisions for Great Plains Energy's regulated operations provide revenue derived from costs including a return on investment of assets and liabilities included in rate base. Except for the significant assets and liabilities for which valuation adjustments were made as discussed above, the fair values of Great Plains Energy's tangible and intangible assets and liabilities subject to these rate-setting provisions approximate their carrying values and the assets and liabilities do not reflect any adjustments to these amounts other than for amounts not included in rate base. The difference between the fair value and pre-merger carrying amounts for Great Plains Energy's long-term debt, asset retirement obligations and pension and post-retirement plans that were related to regulated operations were recorded as a regulatory asset or liability. The excess of the purchase price over the estimated fair values of the assets acquired and liabilities assumed was recognized as goodwill as of the merger date. The preliminary purchase price allocation to Great Plains Energy's assets and liabilities as of June 4, 2018, is detailed in the following table. (millions) Current assets $ 2,151.7 Property, plant and equipment, net 9,179.7 Goodwill 2,338.9 Other long-term assets, excluding goodwill 1,235.9 Total assets $ 14,906.2 Current liabilities 1,673.9 Long-term liabilities, excluding long-term debt 2,898.0 Long-term debt, net 3,358.6 Total liabilities $ 7,930.5 Total purchase price $ 6,975.7 Impact of Merger The impact of Great Plains Energy's subsidiaries on Evergy's revenues in the consolidated statement of comprehensive income for 2018 was an increase of $1,661.1 million . The impact of Great Plains Energy's subsidiaries on Evergy's net income attributable to Evergy in the consolidated statements of comprehensive income for 2018 was an increase of $236.2 million . Evergy has incurred total merger-related costs, including reductions of revenue for customer bill credits, of $148.0 million for 2018 and $11.9 million for 2017. Pro Forma Financial Information The following unaudited pro forma financial information reflects the consolidated results of operations of Evergy as if the merger transactions had taken place on January 1, 2017. The unaudited pro forma information was calculated after applying Evergy's accounting policies and adjusting Great Plains Energy's results to reflect purchase accounting adjustments. The unaudited pro forma financial information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Evergy. 2018 2017 (millions, except per share amounts) Operating revenues $ 5,334.6 $ 5,279.2 Net income attributable to Evergy, Inc. 714.3 468.9 Basic earnings per common share $ 2.67 $ 1.73 Diluted earnings per common share $ 2.67 $ 1.73 Evergy, Westar Energy and Great Plains Energy incurred non-recurring costs and a gain directly related to the merger that have been excluded in the pro forma earnings presented above. On an after-tax basis, these non-recurring merger-related costs and gain incurred by Evergy, Westar Energy and Great Plains Energy included: • $74.7 million and $14.8 million in 2018 and 2017, respectively, of certain after-tax merger-related transition and transaction costs; • $44.4 million in 2018 of after-tax reductions in operating revenues related to one-time customer bill credits; • $278.0 million of after-tax financing charges in 2017 related to Great Plains Energy's previously contemplated acquisition of Westar Energy; and • $36.6 million and $7.3 million in 2018 and 2017, respectively, of after-tax mark-to-market gains on interest rate swaps for which cash settlement was contingent upon the consummation of the merger.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue	3. REVENUE Evergy's, Westar Energy's and KCP&L's revenues disaggregated by customer class are summarized in the following tables. 2018 Evergy Westar Energy KCP&L (a) Revenues (millions) Residential $ 1,578.8 $ 846.4 $ 735.6 Commercial 1,356.4 702.8 794.8 Industrial 527.8 396.4 138.8 Other retail 30.6 20.0 10.4 Total electric retail $ 3,493.6 $ 1,965.6 $ 1,679.6 Wholesale 404.4 346.1 53.5 Transmission 308.1 288.9 14.5 Industrial steam and other 17.9 6.0 4.4 Total revenue from contracts with customers $ 4,224.0 $ 2,606.6 $ 1,752.0 Other 51.9 8.3 71.1 Operating revenues $ 4,275.9 $ 2,614.9 $ 1,823.1 (a) KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018 . Retail Revenues The Evergy Companies' retail revenues are generated by the regulated sale of electricity to their residential, commercial and industrial customers within their franchised service territories. The Evergy Companies recognize revenue on the sale of electricity to their customers over time as the service is provided in the amount they have a right to invoice. Retail customers are billed on a monthly basis at the tariff rates approved by the KCC and MPSC based on customer kWh usage. Revenues recorded include electric services provided but not yet billed by the Evergy Companies. Unbilled revenues are recorded for kWh usage in the period following the customers' billing cycle to the end of the month. This estimate is based on net system kWh usage less actual billed kWhs. The Evergy Companies' estimated unbilled kWhs are allocated and priced by regulatory jurisdiction across the rate classes based on actual billing rates. The Evergy Companies also collect sales taxes and franchise fees from customers concurrent with revenue-producing activities that are levied by state and local governments. These items are excluded from revenue, and thus not reflected on the statements of income and comprehensive income, for Evergy, Westar Energy and KCP&L. Prior to the adoption of ASC 606 on January 1, 2018, KCP&L recorded sales taxes and franchise fees collected from its Missouri customers gross on KCP&L's statements of comprehensive income within operating revenues and taxes other than income taxes. Wholesale Revenues The Evergy Companies' wholesale revenues are generated by the sale of wholesale power and capacity in circumstances when the power that the Evergy Companies generate is not required for customers in their service territory. These sales primarily occur within the SPP Integrated Marketplace. The Evergy Companies also purchase power from the SPP Integrated Marketplace and record sale and purchase activity on a net basis in wholesale revenue or fuel and purchased power expense. In addition, the Evergy Companies sell wholesale power and capacity through bilateral contracts to other counterparties, such as electric cooperatives, municipalities and other electric utilities. For both wholesale sales to the SPP Integrated Marketplace and through bilateral contracts, the Evergy Companies recognize revenue on the sale of wholesale electricity to their customers over time as the service is provided in the amount they have a right to invoice. Wholesale sales within the SPP Integrated Marketplace are billed weekly based on the fixed transaction price determined by the market at the time of the sale and the MWh quantity purchased. Wholesale sales from bilateral contracts are billed monthly based on the contractually determined transaction price and the kWh quantity purchased. Transmission Revenues The Evergy Companies' transmission revenues are generated by the use of their transmission networks by the SPP. To enable optimal use of the diverse generating resources in the SPP region, the Evergy Companies, as well as other transmission owners, allow the SPP to access and operate their transmission networks. As new transmission lines are constructed, they are included in the transmission network available to the SPP. In exchange for providing access, the SPP pays the Evergy Companies consideration determined by formula rates approved by FERC, which include the cost to construct and maintain the transmission lines and a return on investment. The price for access to the Evergy Companies' transmission networks are updated annually based on projected costs. Projections are updated to actual costs and the difference is included in subsequent year's prices. The Evergy Companies have different treatment for their legacy transmission facilities within the SPP, which results in different levels of transmission revenue being received from the SPP. Westar Energy's transmission revenues from SPP include amounts that Westar Energy pays to the SPP on behalf of its retail electric customers for the use of Westar Energy's legacy transmission facilities. These transmission revenues are mostly offset by SPP network transmission cost expense that Westar Energy pays on behalf of its retail customers. KCP&L and GMO do not pay the SPP for their retail customers’ use of the KCP&L and GMO legacy transmission facilities and correspondingly, their transmission revenues also do not reflect the associated transmission revenue from the SPP. The Evergy Companies recognize revenue on the sale of transmission service to their customers over time as the service is provided in the amount they have a right to invoice. Transmission service to the SPP is billed monthly based on a fixed transaction price determined by FERC formula transmission rates along with other SPP-specific charges and the MW quantity purchased. Industrial Steam and Other Revenues Evergy's industrial steam and other revenues are primarily generated by the regulated sale of industrial steam to GMO's steam customers. Evergy recognizes revenue on the sale of industrial steam to its customers over time as the service is provided in the amount that it has the right to invoice. Steam customers are billed on a monthly basis at the tariff rate approved by the MPSC based on customer MMBtu usage. Optional Exemption Evergy, Westar Energy and KCP&L do not disclose the value of unsatisfied performance obligations on certain bilateral wholesale contracts with an original expected duration of greater than one year for which they recognize revenue in the amount they have the right to invoice.

Receivables

Receivables	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Receivables	4 . RECEIVABLES The Evergy Companies' receivables are detailed in the following table. December 31 2018 2017 Evergy (millions) Customer accounts receivable - billed $ 16.7 $ 165.4 Customer accounts receivable - unbilled 91.2 76.6 Other receivables 95.0 55.4 Allowance for doubtful accounts (9.2 ) (6.7 ) Total $ 193.7 $ 290.7 Westar Energy Customer accounts receivable - billed $ — $ 165.4 Customer accounts receivable - unbilled 16.6 76.6 Other receivables 71.6 55.4 Allowance for doubtful accounts (3.9 ) (6.7 ) Total $ 84.3 $ 290.7 KCP&L (a) Customer accounts receivable - billed $ 7.8 $ 1.6 Customer accounts receivable - unbilled 42.9 67.6 Other receivables 15.8 39.3 Allowance for doubtful accounts (3.8 ) (2.2 ) Total $ 62.7 $ 106.3 (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017. Evergy's, Westar Energy's and KCP&L's other receivables at December 31, 2018 and 2017, consisted primarily of receivables from partners in jointly-owned electric utility plants and wholesale sales receivables. As of December 31, 2018 , other receivables for Evergy, Westar Energy and KCP&L included receivables from contracts with customers of $65.8 million , $55.9 million and $5.5 million , respectively. The Evergy Companies recorded bad debt expense related to contracts with customers as summarized in the following table. 2018 2017 2016 (millions) Evergy $ 20.2 $ 10.3 $ 11.4 Westar Energy 8.5 10.3 11.4 KCP&L (a) 13.1 7.6 6.3 (a) KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018 . Sale of Accounts Receivable Westar Energy, KCP&L and GMO sell an undivided percentage ownership interest in their retail electric and certain other accounts receivable to independent outside investors. These sales of the undivided percentage ownership interests in accounts receivable to independent outside investors are accounted for as secured borrowings with accounts receivable pledged as collateral and a corresponding short-term collateralized note payable recognized on the balance sheets. At December 31, 2018 , Evergy's accounts receivable pledged as collateral and the corresponding short-term collateralized note payable were $365.0 million . At December 31, 2018 , Westar Energy's accounts receivable pledged as collateral and the corresponding short-term collateralized note payable were $185.0 million . At December 31, 2018 and 2017 , KCP&L's accounts receivable pledged as collateral and the corresponding short-term collateralized note payable were $130.0 million . Westar Energy's receivable sale facility expires in September 2019 and allows for $185.0 million in aggregate outstanding principal amount of borrowings from mid-December through mid-January, $125.0 million from mid January through mid-February, $185.0 million from mid-February to mid-July and then $200.0 million from mid-July through the expiration date of the facility. KCP&L's receivable sale facility expires in September 2019 and allows for $130.0 million in aggregate outstanding principal amount of borrowings at any time. GMO's receivable sale facility expires in September 2019 and allows for $50.0 million in aggregate outstanding principal amount of borrowings from mid-November through mid-June and then $65.0 million from mid-June through the expiration date of the facility.

Rate Matters and Regulation

Rate Matters and Regulation	12 Months Ended
	Dec. 31, 2018
Regulated Operations [Abstract]
Rate Matters and Regulation	5 . RATE MATTERS AND REGULATION KCC Proceedings Westar Energy 2018 Transmission Delivery Charge In March 2018, the KCC issued an order adjusting Westar Energy's retail prices to include updated transmission costs as reflected in the FERC transmission formula rate (TFR). The new prices were effective in April 2018 and are expected to increase Westar Energy's annual retail revenues by $31.5 million . In August 2018, Westar Energy filed an updated Transmission Delivery Charge (TDC) tariff with the KCC to reflect the reduction in revenue requirement that occurred as a result of the Tax Cuts and Jobs Act (TCJA). The updated filing requested new prices decreasing Westar Energy's annual retail revenues by approximately $20 million . In October 2018, the KCC issued an order approving the request with the new prices effective October 30, 2018. Westar Energy 2018 Rate Case Proceedings In February 2018, Westar Energy filed an application with the KCC to request a two-step change in rates, a decrease to retail revenues of approximately $2 million in September 2018 followed by an increase in retail revenues of approximately $54 million in February 2019, with a return on equity of 9.85% and a rate-making equity ratio of 51.6% . The request reflects costs associated with the completion of the Western Plains Wind Farm, the expiration of wholesale contracts currently reflected in retail prices as offsets to retail cost of service, the expiration of production tax credits from prior wind investments and an updated depreciation study, partially offset by the impact of the TCJA and a portion of the savings from the merger with Great Plains Energy. In July 2018, Westar Energy, the KCC staff and several other intervenors in the case reached a non-unanimous stipulation and agreement to settle all outstanding issues in the case. The stipulation and agreement provides for a decrease to retail revenues of $66.0 million , before rebasing property tax expense, with a return on equity of 9.3% , a rate-making equity ratio of 51.46% and does not include a second step revenue requirement change as included in Westar Energy's initial application. The stipulation and agreement also provides for an approximately $16 million increase associated with rebasing property tax expense, an approximately $46 million increase in depreciation expense, allows for the recovery of an approximately $41 million wholesale contract that expires in 2019 through Westar Energy's fuel recovery mechanism and reflects customer benefits related to the impacts of the TCJA, including a one-time bill credit of approximately $50 million , which was provided to customers following the conclusion of the rate case. In September 2018, the KCC issued an order approving the non-unanimous stipulation and agreement. The rates established by the order took effect on September 27, 2018. KCP&L 2018 Rate Case Proceedings In May 2018, KCP&L filed an application with the KCC to request an increase to its retail revenues of $26.2 million before rebasing property tax expense, with a return on equity of 9.85% and a rate-making equity ratio of 49.8% . The request reflects the impact of the TCJA and increases in infrastructure investment costs. KCP&L also requested an additional $6.7 million increase associated with rebasing property tax expense. In October 2018, KCP&L, the KCC staff and other intervenors reached a unanimous settlement agreement to settle all outstanding issues in the case. The settlement agreement provides for a decrease to retail revenues of $3.9 million , a return on equity of 9.3% , a rate-making equity ratio of 49.09% and a one-time bill credit of $36.9 million for customer benefits related to the impacts of the TCJA. In December 2018, KCC issued an order approving the unanimous settlement agreement. The rates established by the order took effect on December 20, 2018. MPSC Proceedings KCP&L 2018 Rate Case Proceedings In January 2018, KCP&L filed an application with the MPSC to request an increase to its retail revenues of $8.9 million before rebasing fuel and purchased power expense, with a return on equity of 9.85% and a rate-making equity ratio of 50.03% . The request reflects the impact of the TCJA and increases in infrastructure investment costs, transmission related costs and property tax costs. KCP&L also requested an additional $7.5 million increase associated with rebasing fuel and purchased power expense. In September 2018, KCP&L, MPSC staff and other intervenors in the case reached several non-unanimous stipulations and agreements to settle all outstanding issues in the case. The stipulations and agreements provide for a decrease to retail revenues of $21.1 million and a one-time customer benefit of $38.7 million (on an annualized basis) related to the impact of the TCJA, which will be offset against existing KCP&L regulatory assets. The final amount of the one-time customer benefit related to the impact of the TCJA was $36.4 million , as its calculation was dependent on the effective date of new rates. In October 2018, the MPSC issued an order approving the non-unanimous stipulations and agreements. The rates established by the order took effect on December 6, 2018. GMO 2018 Rate Case Proceedings In January 2018, GMO filed an application with the MPSC to request a decrease to its retail revenues of $2.4 million before rebasing fuel and purchased power expense, with a return on equity of 9.85% and a rate-making equity ratio of 54.4% . The request reflects the impact of the TCJA and increases in infrastructure investment costs and transmission related costs. GMO also requested a $21.7 million increase associated with rebasing fuel and purchased power expense. In September 2018, GMO, MPSC staff and other intervenors in the case reached several non-unanimous stipulations and agreements to settle all outstanding issues in the case. The stipulations and agreements provide for a decrease to retail revenues of $24.0 million and a one-time bill credit of $29.3 million (on an annualized basis) for customer benefits related to the impacts of the TCJA. The final amount of the one-time customer bill credit related to the impact of the TCJA was $27.4 million , as its calculation was dependent on the effective date of new rates. In October 2018, the MPSC issued an order approving the non-unanimous stipulations and agreements. The rates established by the order took effect on December 6, 2018. FERC Proceedings In October of each year, Westar Energy posts an updated TFR that includes projected transmission capital expenditures and operating costs for the following year. This rate provides the basis for Westar Energy's annual request with the KCC to adjust retail prices to include updated transmission costs. In the most recent three years, the updated TFR was expected to adjust Westar Energy's annual transmission revenues by approximately: • $11.2 million decrease effective in January 2019; • $2.3 million increase effective in January 2018 ( $25.5 million increase offset by $23.2 million decrease from reduction in federal corporate income tax rate); and • $29.6 million increase effective in January 2017. Regulatory Assets and Liabilities The Evergy Companies have recorded assets and liabilities on their consolidated balance sheets resulting from the effects of the ratemaking process, which would not otherwise be recorded if they were not regulated. Regulatory assets represent incurred costs that are probable of recovery from future revenues. Regulatory liabilities represent future reductions in revenues or refunds to customers. Management regularly assesses whether regulatory assets and liabilities are probable of future recovery or refund by considering factors such as decisions by the MPSC, KCC or FERC in Westar Energy's, KCP&L's and GMO's rate case filings; decisions in other regulatory proceedings, including decisions related to other companies that establish precedent on matters applicable to the Evergy Companies; and changes in laws and regulations. If recovery or refund of regulatory assets or liabilities is not approved by regulators or is no longer deemed probable, these regulatory assets or liabilities are recognized in the current period results of operations. The Evergy Companies continued ability to meet the criteria for recording regulatory assets and liabilities may be affected in the future by restructuring and deregulation in the electric industry or changes in accounting rules. In the event that the criteria no longer applied to any or all of the Evergy Companies' operations, the related regulatory assets and liabilities would be written off unless an appropriate regulatory recovery mechanism were provided. Additionally, these factors could result in an impairment on utility plant assets. The Evergy Companies' regulatory assets and liabilities are detailed in the following table. December 31 2018 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (a) Regulatory Assets (millions) Pension and post-retirement costs $ 808.2 $ 343.7 $ 361.5 $ 393.9 $ 393.9 $ 379.7 Debt reacquisition costs 113.5 104.1 8.2 109.2 109.2 8.7 Debt fair value adjustment 134.5 — — — — — Asset retirement obligations fair value 111.4 — — — — — Depreciation 58.0 58.0 — 60.6 60.6 — Cost of removal 102.4 65.7 36.7 30.8 30.8 30.3 Asset retirement obligations 171.9 49.5 91.6 42.7 42.7 94.3 Analog meter unrecovered investment 35.6 35.6 — 31.5 31.5 — Treasury yield hedges 23.7 23.7 — 24.8 24.8 — Iatan No. 1 and common facilities 7.4 — 2.9 — — 12.9 Iatan No. 2 construction accounting costs 26.8 — 13.5 — — 25.0 Kansas property tax surcharge 33.1 23.7 9.4 17.4 17.4 6.6 Disallowed plant costs 15.0 15.0 — 15.2 15.2 — La Cygne environmental costs 14.8 12.2 2.6 13.3 13.3 2.7 Deferred customer programs 19.9 7.0 8.0 8.1 8.1 40.9 Fuel recovery mechanisms 91.2 7.1 41.7 20.7 20.7 61.7 Solar rebates 45.2 — 13.9 — — 22.6 Transmission delivery charge 0.8 — 0.8 — — 3.2 Wolf Creek outage 21.8 10.9 10.9 7.0 7.0 6.8 Pension and other post-retirement benefit 13.6 5.2 4.8 — — — Retired generation facilities 159.9 — — — — — Merger transition costs 47.0 22.6 17.3 — — — Other regulatory assets 6.1 13.5 2.3 9.7 9.7 3.3 Total 2,061.8 797.5 626.1 784.9 784.9 698.7 Less: current portion (303.9 ) (97.1 ) (130.9 ) (99.5 ) (99.5 ) (153.6 ) Total noncurrent regulatory assets $ 1,757.9 $ 700.4 $ 495.2 $ 685.4 $ 685.4 $ 545.1 (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017. December 31 2018 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (a) Regulatory Liabilities (millions) Taxes refundable through future rates $ 1,703.6 $ 853.2 $ 609.2 $ 845.2 $ 845.2 $ 574.0 Deferred regulatory gain from sale 59.1 59.1 — 64.6 64.6 — Emission allowances 54.1 — 54.1 — — 58.1 Nuclear decommissioning 188.2 84.5 103.7 55.5 55.5 126.0 Pension and post-retirement costs 53.4 28.3 25.1 48.4 48.4 12.0 Jurisdictional allowance for funds used 30.3 30.3 — 31.7 31.7 — La Cygne leasehold dismantling costs 29.5 29.5 — 29.6 29.6 — Cost of removal 48.1 — — — — — Kansas tax credits 16.5 16.5 — 16.8 16.8 — Purchase power agreement 8.8 8.8 — 8.8 8.8 — Merger customer credits 7.5 — 7.5 — — — Refund of tax reform benefits 70.9 7.2 36.3 — — — Other regulatory liabilities 59.0 3.9 11.2 5.0 5.0 9.1 Total 2,329.0 1,121.3 847.1 1,105.6 1,105.6 779.2 Less: current portion (110.2 ) (19.5 ) (52.8 ) (11.6 ) (11.6 ) (8.3 ) Total noncurrent regulatory liabilities $ 2,218.8 $ 1,101.8 $ 794.3 $ 1,094.0 $ 1,094.0 $ 770.9 (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017. The following summarizes the nature and period of recovery for each of the regulatory assets listed in the table above. Pension and post-retirement costs: Represents unrecognized gains and losses, prior service and transition costs that will be recognized in future net periodic pension and post-retirement costs, pension settlements amortized over various periods and financial and regulatory accounting method differences that will be eliminated over the life of the pension plans. Of these amounts, $764.5 million , $343.7 million and $353.6 million for Evergy, Westar Energy and KCP&L, respectively, are not included in rate base and are amortized over various periods. Debt reacquisition costs: Includes costs incurred to reacquire and refinance debt. These costs are amortized over the term of the new debt or the remaining lives of the old debt issuances if no new debt was issued and are not included in rate base. Debt fair value adjustment: Represents purchase accounting adjustments recorded to state the carrying value of KCP&L and GMO long-term debt at fair value in connection with the merger. Amount is amortized over the life of the related debt and is not included in rate base. Asset retirement obligations fair value adjustment: Represents purchase accounting adjustments recorded to state the carrying value of KCP&L and GMO AROs at fair value in connection with the merger. Amount is amortized over the life of the related plant and is not included in rate base. Depreciation: Represents the difference between regulatory depreciation expense and depreciation expense recorded for financial reporting purposes. These assets are included in rate base and the difference is amortized over the life of the related plant. Cost of removal: Represents amounts spent, but not yet collected, to dispose of plant assets. This asset will decrease as removal costs are collected in rates and is not included in rate base. Asset retirement obligations: Represents amounts associated with AROs as discussed further in Note 6 . These amounts are recovered over the life of the related plant and are not included in rate base. Analog meter unrecovered investment: Represents the deferral of unrecovered investment of retired analog meters. Of this amount, $27.3 million is not included in rate base for Evergy and Westar Energy and is being amortized over a five -year period. Treasury yield hedges: Represents the effective portion of treasury yield hedge transactions. Amortization of this amount will be included in interest expense over the term of the related debt and is not included in rate base. Iatan No. 1 and common facilities: Represents depreciation and carrying costs related to Iatan No. 1 and common facilities. These costs are included in rate base and amortized over various periods. Iatan No. 2 construction accounting costs: Represents the construction accounting costs related to Iatan No. 2. These costs are included in rate base and amortized through 2059 . Kansas property tax surcharge: Represents actual costs incurred for property taxes in excess of amounts collected in revenues. These costs are expected to be recovered over a one -year period and are not included in rate base. Disallowed plant costs: The KCC originally disallowed certain costs related to the Wolf Creek plant. In 1987, the KCC revised its original conclusion and provided for recovery of an indirect disallowance with no return on investment. This regulatory asset represents the present value of the future expected revenues to be provided to recover these costs, net of the amounts amortized. La Cygne environmental costs: Represents the deferral of depreciation and amortization expense and associated carrying charges related to the La Cygne Station environmental project. This amount will be amortized over the life of the related asset and is included in rate base. Deferred customer programs: Represents costs related to various energy efficiency programs that have been accumulated and deferred for future recovery. Of these amounts, $4.7 million for Evergy and KCP&L are not included in rate base and are amortized over various periods. Fuel recovery mechanisms: Represents the actual cost of fuel consumed in producing electricity and the cost of purchased power in excess of the amounts collected from customers. This difference is expected to be recovered over a one -year period and is not included in rate base. Solar rebates: Represents costs associated with solar rebates provided to retail electric customers. These amounts are not included in rate base and are amortized through 2020 . Transmission delivery charge: Represents costs associated with the transmission delivery charge. The amounts are not included in rate base and are amortized over a one -year period. Wolf Creek outage: Represents deferred expenses associated with Wolf Creek's scheduled refueling and maintenance outages. These expenses are amortized during the period between planned outages and are not included in rate base. Pension and other post-retirement benefit non-service costs: Represents the non-service component of pension and post-retirement net benefit costs that are capitalized as authorized by regulators. The amounts are included in rate base and are recovered over the life of the related asset. Retired generation facilities: Represents amounts to be recovered for facilities that have been retired and are probable of recovery. Merger transition costs: Represents recoverable transition costs related to the merger. The amounts are not included in rate base and are recovered from retail customers through 2028 . Other regulatory assets: Includes various regulatory assets that individually are small in relation to the total regulatory asset balance. These amounts have various recovery periods and are not included in rate base. The following summarizes the nature and period of amortization for each of the regulatory liabilities listed in the table above. Taxes refundable through future rates: Represents the obligation to return to customers income taxes recovered in earlier periods when corporate income tax rates were higher than current income tax rates. A large portion of this amount is related to depreciation and will be returned to customers over the life of the applicable property. Deferred regulatory gain from sale leaseback: Represents the gain KGE recorded on the 1987 sale and leaseback of its 50% interest in La Cygne Unit 2. The gain is amortized over the term of the lease. Emission allowances: Represents deferred gains related to the sale of emission allowances to be returned to customers. Nuclear decommissioning: Represents the difference between the fair value of the assets held in the nuclear decommissioning trust and the amount recorded for the accumulated accretion and depreciation expense associated with the asset retirement obligation related to Wolf Creek. Pension and post-retirement costs: Includes pension and post-retirement benefit obligations and expense recognized in setting prices in excess of actual pension and post-retirement expense. Jurisdictional allowance for funds used during construction: Represents AFUDC that is accrued subsequent to the time the associated construction charges are included in prices and prior to the time the related assets are placed in service. The AFUDC is amortized to depreciation expense over the useful life of the asset that is placed in service. La Cygne leasehold dismantling costs: Represents amounts collected but not yet spent on the contractual obligation to dismantle a portion of La Cygne Unit 2. The obligation will be discharged as the unit is dismantled. Cost of removal: Represents amount collected, but not yet spent, to dispose of plant assets. This liability will be discharged as removal costs are incurred. Kansas tax credits: Represents Kansas tax credits on investment in utility plant. Amounts will be credited to customers subsequent to the realization of the credits over the remaining lives of the utility plant giving rise to the tax credits. Purchase power agreement: Represents the amount included in retail electric rates from customers in excess of costs incurred under purchase power agreements. Amounts are amortized over a five -year period. Merger customer credits: Represents one-time merger bill credits to KCP&L's Kansas electric retail customers. The credits are expected to be provided to customers in the first quarter of 2019. Refund of tax reform benefits: Represents amounts collected from customers in 2018 related to federal income tax in excess of the income tax owed by the Evergy Companies as a result of the lower federal income tax rate enacted by the TCJA. Amounts will be refunded to customers in 2019. Other regulatory liabilities: Includes various regulatory liabilities that individually are relatively small in relation to the total regulatory liability balance. These amounts will be credited over various periods.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	6 . ASSET RETIREMENT OBLIGATIONS AROs associated with tangible long-lived assets are legal obligations that exist under enacted laws, statutes and written or oral contracts, including obligations arising under the doctrine of promissory estoppel. These liabilities are recognized at estimated fair value as incurred with a corresponding amount capitalized as part of the cost of the related long-lived assets and depreciated over their useful lives. Accretion of the liabilities due to the passage of time is recorded to a regulatory asset and/or liability. Changes in the estimated fair values of the liabilities are recognized when known. Westar Energy, KCP&L and GMO have AROs related to asbestos abatement and the closure and post-closure care of ponds and landfills containing coal combustion residuals (CCRs). In addition, Westar Energy and KCP&L have AROs related to decommissioning Wolf Creek Generating Station (Wolf Creek) and the retirement of wind generation facilities. The following table summarizes the change in the Evergy Companies' AROs. Evergy Westar Energy KCP&L (a) 2018 2017 2018 2017 2018 2017 (millions) Beginning balance $ 405.1 $ 324.0 $ 405.1 $ 324.0 $ 266.3 $ 278.0 Liabilities assumed upon merger with Great Plains Energy 412.2 — — — — — Liabilities incurred during the year 7.4 13.5 7.4 13.5 — — Revision in timing and/or estimates (150.1 ) 66.8 (138.7 ) 66.8 (11.4 ) 0.3 Settlements (22.4 ) (16.0 ) (12.0 ) (16.0 ) (13.1 ) (25.5 ) Accretion 34.9 16.8 19.3 16.8 19.2 13.5 Ending balance $ 687.1 $ 405.1 $ 281.1 $ 405.1 $ 261.0 $ 266.3 Less: current portion (49.8 ) (25.1 ) (17.1 ) (25.1 ) (29.2 ) (34.9 ) Total noncurrent asset retirement obligation $ 637.3 $ 380.0 $ 264.0 $ 380.0 $ 231.8 $ 231.4 (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018 . See Note 2 for more information regarding KCP&L's and GMO's ARO liabilities that Evergy assumed as a result of the merger. In 2018, Evergy and Westar Energy recorded a $127.0 million revision in estimate primarily related to Westar Energy's ARO to decommission its 47% ownership share of Wolf Creek.

Property, Plant & Equipment Pro

Property, Plant & Equipment Property, Plant & Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Disclosure [Text Block]	7 . PROPERTY, PLANT AND EQUIPMENT The following tables summarize the property, plant and equipment of Evergy, Westar Energy and KCP&L. December 31, 2018 Evergy Westar Energy KCP&L (millions) Electric plant in service $ 26,916.7 $ 13,176.7 $ 10,439.1 Electric plant acquisition adjustment 740.6 740.6 — Accumulated depreciation (9,694.1 ) (4,642.8 ) (4,022.4 ) Plant in service 17,963.2 9,274.5 6,416.7 Construction work in progress 685.2 376.7 204.4 Nuclear fuel, net 133.1 66.1 67.0 Plant to be retired, net (b) 1.0 1.0 — Net property, plant and equipment $ 18,782.5 $ 9,718.3 $ 6,688.1 December 31, 2017 Evergy Westar Energy KCP&L (a) (millions) Electric plant in service $ 12,954.3 $ 12,954.3 $ 10,213.2 Electric plant acquisition adjustment 739.0 739.0 — Accumulated depreciation (4,651.7 ) (4,651.7 ) (4,070.3 ) Plant in service 9,041.6 9,041.6 6,142.9 Construction work in progress 434.9 434.9 350.3 Nuclear fuel, net 71.4 71.4 72.4 Plant to be retired, net (b) 5.9 5.9 — Net property, plant and equipment $ 9,553.8 $ 9,553.8 $ 6,565.6 (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017. (b) As of December 31, 2018 and 2017, represents the planned retirement of Westar Energy analog meters prior to the end of their remaining useful lives. The following table summarizes the property, plant and equipment of VIEs for Evergy and Westar Energy. December 31 2018 2017 (millions) Electric plant of VIEs $ 392.1 $ 392.1 Accumulated depreciation of VIEs (222.9 ) (215.8 ) Net property, plant and equipment of VIEs $ 169.2 $ 176.3 Depreciation Expense The Evergy Companies' depreciation expense is detailed in the following table. 2018 2017 2016 (millions) Evergy (a) $ 567.9 $ 350.0 $ 316.7 Westar Energy (a) 371.3 350.0 316.7 KCP&L 235.3 228.4 215.4 (a) Approximately $7.1 million , $8.3 million and $9.5 million of depreciation expense in 2018 , 2017 and 2016 , respectively, was attributable

Jointly Owned Electric Utility

Jointly Owned Electric Utility Plants	12 Months Ended
	Dec. 31, 2018
Jointly Owned Electric Utility Plants [Abstract]
Jointly Owned Electric Utility Plants [Text Block]	8. JOINTLY-OWNED ELECTRIC UTILITY PLANTS Evergy's, Westar Energy's and KCP&L's share of jointly-owned electric utility plants at December 31, 2018 , are detailed in the following tables. Evergy Wolf Creek Unit La Cygne Units (a) Iatan No. 1 Unit Iatan No. 2 Unit Iatan Common Jeffrey Energy Center (b) State Line (millions, except MW amounts) Evergy's share 94% 100% 88% 73% 79% 100% 40% Utility plant in service $ 3,724.9 $ 2,228.0 $ 707.3 $ 1,374.5 $ 504.9 $ 2,392.5 $ 114.1 Accumulated depreciation 1,760.8 737.1 257.3 426.7 127.8 861.0 71.3 Nuclear fuel, net 133.1 — — — — — — Construction work in progress 171.6 41.8 27.1 30.5 26.5 33.2 0.4 2019 accredited capacity-MWs 1,104 1,398 616 641 NA 2,187 196 (a) The VIE consolidated by Evergy and Westar Energy holds its 50% leasehold interest in La Cygne Unit 2. This 50% leasehold interest in La Cygne Unit 2 is reflected in the information provided above. See Note 7 for additional information. (b) Evergy and Westar Energy's 8% leasehold interest in Jeffrey Energy Center is reflected in the information provided above. Westar Energy Wolf Creek Unit La Cygne Units (a) Jeffrey Energy Center (b) State Line (millions, except MW amounts) Westar Energy's share 47% 50% 92% 40% Utility plant in service $ 1,833.7 $ 1,033.5 $ 2,189.6 $ 114.1 Accumulated depreciation 825.3 408.6 778.6 71.3 Nuclear fuel, net 66.1 — — — Construction work in progress 83.7 34.0 30.6 0.4 2019 accredited capacity-MWs 552 699 2,012 196 (a) The VIE consolidated by Evergy and Westar Energy holds its 50% leasehold interest in La Cygne Unit 2. This 50% leasehold interest in La Cygne Unit 2 is reflected in the information provided above. See Note 7 for additional information. (b) Evergy's and Westar Energy's 8% leasehold interest in Jeffrey Energy Center is reflected in the information provided above. KCP&L Wolf Creek Unit La Cygne Units Iatan No. 1 Unit Iatan No. 2 Unit Iatan Common (millions, except MW amounts) KCP&L's share 47% 50% 70% 55% 61% Utility plant in service $ 1,891.2 $ 1,194.5 $ 567.4 $ 1,060.3 $ 414.8 Accumulated depreciation 935.5 328.5 203.2 378.4 112.8 Nuclear fuel, net 67.0 — — — — Construction work in progress 87.9 7.8 3.3 6.2 15.0 2019 accredited capacity-MWs 552 699 490 482 NA Each owner must fund its own portion of the plant's operating expenses and capital expenditures. The Evergy Companies' share of direct expenses are included in the appropriate operating expense classifications in Evergy's, Westar Energy's and KCP&L's consolidated financial statements.

Pension Plans and Other Employe

Pension Plans and Other Employee Benefits	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Pension Plans and Other Employee Benefits	9 . PENSION PLANS AND POST-RETIREMENT BENEFITS Evergy and certain of its subsidiaries maintain, and Westar Energy and KCP&L participate in, qualified non-contributory defined benefit pension plans covering the majority of Westar Energy's and KCP&L's employees as well as certain non-qualified plans covering certain active and retired officers. Evergy is also responsible for its 94% ownership share of Wolf Creek's defined benefit plans, consisting of Westar Energy's and KCP&L's respective 47% ownership shares. For the majority of employees, pension benefits under these plans reflect the employees' compensation, years of service and age at retirement. However, for the plan covering Westar Energy's employees, the benefits for non-union employees hired between 2002 and the second quarter of 2018 and union employees hired beginning in 2012 are derived from a cash balance account formula. The plan was closed to future non-union employees in 2018. For the plans covering KCP&L's employees, the benefits for union employees hired beginning in 2014 are derived from a cash balance account formula and the plans were closed to future non-union employees in 2014. Evergy and its subsidiaries also provide certain post-retirement health care and life insurance benefits for substantially all retired employees of Westar Energy and KCP&L and their respective shares of Wolf Creek's post-retirement benefit plans. The Evergy Companies record pension and post-retirement expense in accordance with rate orders from the KCC and MPSC that allow the difference between pension and post-retirement costs under GAAP and costs for ratemaking to be recognized as a regulatory asset or liability. This difference between financial and regulatory accounting methods is due to timing and will be eliminated over the life of the plans. The following pension benefits tables provide information relating to the funded status of all defined benefit pension plans on an aggregate basis as well as the components of net periodic benefit costs. For financial reporting purposes, the market value of plan assets is the fair value. Net periodic benefit costs reflect total plan benefit costs prior to the effects of capitalization and sharing with joint owners of power plants. KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018. Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Change in projected benefit obligation (PBO) (millions) PBO at January 1, 2018 $ 1,367.0 $ 1,367.0 $ 1,331.7 $ 138.6 $ 138.6 $ 133.2 Service cost 60.7 32.2 48.6 2.3 1.3 2.0 Interest cost 82.5 50.7 49.9 8.0 5.0 4.8 Contribution by participants — — — 5.6 1.8 6.6 Plan amendments 13.4 11.4 2.0 — — — Actuarial (gain) loss (98.8 ) (100.1 ) (89.6 ) (11.3 ) (2.6 ) (18.0 ) Benefits paid (137.9 ) (97.9 ) (70.2 ) (17.3 ) (10.5 ) (12.9 ) Obligations assumed upon merger with Great Plains Energy 1,275.9 — — 123.4 — — Other (9.4 ) (4.4 ) — — — — PBO at December 31, 2018 $ 2,553.4 $ 1,258.9 $ 1,272.4 $ 249.3 $ 133.6 $ 115.7 Change in plan assets Fair value of plan assets at January 1, 2018 $ 887.0 $ 887.0 $ 848.4 $ 124.1 $ 124.1 $ 115.8 Actual return on plan assets (79.7 ) (30.9 ) (60.1 ) (7.5 ) (7.4 ) (1.2 ) Contributions by employer and participants 114.5 47.9 80.3 11.6 3.2 11.4 Benefits paid (134.0 ) (95.0 ) (69.8 ) (16.7 ) (10.2 ) (12.4 ) Assets acquired upon merger with Great Plains Energy 825.0 — — 111.8 — — Other (9.4 ) (4.4 ) — — — — Fair value of plan assets at December 31, 2018 $ 1,603.4 $ 804.6 $ 798.8 $ 223.3 $ 109.7 $ 113.6 Funded status at December 31, 2018 $ (950.0 ) $ (454.3 ) $ (473.6 ) $ (26.0 ) $ (23.9 ) $ (2.1 ) Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Amounts recognized in the consolidated balance sheets (millions) Non-current asset $ — $ — $ — $ 17.5 $ — $ 17.5 Current pension and other post-retirement liability (4.4 ) (2.6 ) (0.5 ) (1.7 ) (0.9 ) (0.8 ) Noncurrent pension liability and other post-retirement liability (945.6 ) (451.7 ) (473.1 ) (41.8 ) (23.0 ) (18.8 ) Net amount recognized before regulatory treatment (950.0 ) (454.3 ) (473.6 ) (26.0 ) (23.9 ) (2.1 ) Accumulated OCI or regulatory asset/liability 419.9 337.5 362.4 (6.0 ) 0.8 (26.0 ) Net amount recognized at December 31, 2018 $ (530.1 ) $ (116.8 ) $ (111.2 ) $ (32.0 ) $ (23.1 ) $ (28.1 ) Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost: Actuarial (gain) loss $ 403.6 $ 323.2 $ 226.3 $ (7.8 ) $ (1.0 ) $ (11.0 ) Prior service cost 16.3 14.3 3.8 1.8 1.8 (8.1 ) Other — — 132.3 — — (6.9 ) Net amount recognized at December 31, 2018 $ 419.9 $ 337.5 $ 362.4 $ (6.0 ) $ 0.8 $ (26.0 ) Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Change in projected benefit obligation (PBO) (millions) PBO at January 1, 2017 $ 1,241.0 $ 1,241.0 $ 1,220.6 $ 136.8 $ 136.8 $ 130.1 Service cost 28.7 28.7 44.2 1.2 1.2 2.1 Interest cost 52.4 52.4 52.6 5.5 5.5 5.4 Contribution by participants — — — 1.5 1.5 6.0 Actuarial loss 107.0 107.0 134.9 2.8 2.8 2.1 Benefits paid (62.1 ) (62.1 ) (34.7 ) (9.2 ) (9.2 ) (12.5 ) Settlements and special termination benefits — — (85.9 ) — — — PBO at December 31, 2017 $ 1,367.0 $ 1,367.0 $ 1,331.7 $ 138.6 $ 138.6 $ 133.2 Change in plan assets Fair value of plan assets at January 1, 2017 $ 797.2 $ 797.2 $ 776.8 $ 115.6 $ 115.6 $ 115.6 Actual return on plan assets 113.1 113.1 114.8 15.6 15.6 1.8 Contributions by employer and participants 36.3 36.3 76.9 1.9 1.9 10.4 Benefits paid (59.6 ) (59.6 ) (34.5 ) (9.0 ) (9.0 ) (12.0 ) Settlements — — (85.6 ) — — — Fair value of plan assets at December 31, 2017 $ 887.0 $ 887.0 $ 848.4 $ 124.1 $ 124.1 $ 115.8 Funded status at December 31, 2017 $ (480.0 ) $ (480.0 ) $ (483.3 ) $ (14.5 ) $ (14.5 ) $ (17.4 ) Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Amounts recognized in the consolidated balance sheets (millions) Non-current asset $ — $ — $ — $ — $ — $ 12.8 Current pension and other post-retirement liability (2.5 ) (2.5 ) (0.6 ) (0.8 ) (0.8 ) (0.8 ) Noncurrent pension liability and other post-retirement liability (477.5 ) (477.5 ) (482.7 ) (13.7 ) (13.7 ) (29.4 ) Net amount recognized before regulatory treatment (480.0 ) (480.0 ) (483.3 ) (14.5 ) (14.5 ) (17.4 ) Accumulated OCI or regulatory asset/liability 372.6 372.6 379.7 (11.1 ) (11.1 ) (12.2 ) Net amount recognized at December 31, 2017 $ (107.4 ) $ (107.4 ) $ (103.6 ) $ (25.6 ) $ (25.6 ) $ (29.6 ) Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost: Actuarial (gain) loss $ 369.0 $ 369.0 $ 245.5 $ (13.3 ) $ (13.3 ) $ 2.8 Prior service cost 3.6 3.6 2.5 2.2 2.2 (8.0 ) Other — — 131.7 — — (7.0 ) Net amount recognized at December 31, 2017 $ 372.6 $ 372.6 $ 379.7 $ (11.1 ) $ (11.1 ) $ (12.2 ) As of December 31, 2018 and 2017, Evergy's pension benefits include non-qualified benefit obligations of $46.9 million and $27.4 million , respectively, which are funded by trusts containing assets of $43.8 million and $34.3 million , respectively. As of December 31, 2018 and 2017, Westar Energy's pension benefits include non-qualified benefit obligations of $24.8 million and $27.4 million , respectively, which are funded by trusts containing assets of $30.6 million and $34.3 million , respectively. The assets in the aforementioned trusts are not included in the table above. See Note 13 for more information on these amounts. Pension Benefits Post-Retirement Benefits Year Ended December 31, 2018 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Components of net periodic benefit costs (millions) Service cost $ 60.7 $ 32.2 $ 48.6 $ 2.3 $ 1.3 $ 2.0 Interest cost 82.5 50.7 49.9 8.0 5.0 4.8 Expected return on plan assets (86.4 ) (55.9 ) (55.5 ) (8.8 ) (7.0 ) (2.8 ) Prior service cost 0.7 0.7 0.7 0.5 0.5 0.1 Recognized net actuarial (gain) loss 32.6 32.6 45.1 (0.6 ) (0.6 ) (0.2 ) Net periodic benefit costs before regulatory adjustment and intercompany allocations 90.1 60.3 88.8 1.4 (0.8 ) 3.9 Regulatory adjustment 8.3 8.8 0.7 (1.7 ) (2.0 ) (0.1 ) Intercompany allocations n/a — (21.6 ) n/a — (1.1 ) Net periodic benefit costs 98.4 69.1 67.9 (0.3 ) (2.8 ) 2.7 Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities Current year net (gain) loss 67.2 (13.2 ) 25.9 4.9 11.7 (14.0 ) Amortization of gain (loss) (32.6 ) (32.6 ) (45.1 ) 0.6 0.6 0.2 Prior service cost 13.4 11.4 2.0 — — — Amortization of prior service cost (0.7 ) (0.7 ) (0.7 ) (0.5 ) (0.5 ) (0.1 ) Other regulatory activity — — 0.6 — — — Total recognized in OCI or regulatory asset/liability 47.3 (35.1 ) (17.3 ) 5.0 11.8 (13.9 ) Total recognized in net periodic benefit costs and OCI or regulatory asset/liability $ 145.7 $ 34.0 $ 50.6 $ 4.7 $ 9.0 $ (11.2 ) Pension Benefits Post-Retirement Benefits Year Ended December 31, 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Components of net periodic benefit costs (millions) Service cost $ 28.7 $ 28.7 $ 44.2 $ 1.2 $ 1.2 $ 2.1 Interest cost 52.4 52.4 52.6 5.5 5.5 5.4 Expected return on plan assets (53.6 ) (53.6 ) (51.2 ) (6.9 ) (6.9 ) (2.5 ) Prior service cost 0.7 0.7 0.7 0.5 0.5 — Recognized net actuarial (gain) loss 26.9 26.9 49.0 (0.8 ) (0.8 ) (0.5 ) Settlement and special termination benefits 0.4 0.4 16.3 — — — Net periodic benefit costs before regulatory adjustment and intercompany allocations 55.5 55.5 111.6 (0.5 ) (0.5 ) 4.5 Regulatory adjustment 14.5 14.5 (9.2 ) (1.9 ) (1.9 ) 1.3 Intercompany allocations n/a — (37.1 ) n/a — (1.5 ) Net periodic benefit costs 70.0 70.0 65.3 (2.4 ) (2.4 ) 4.3 Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities Current year net (gain) loss 47.1 47.1 71.3 (5.8 ) (5.8 ) 3.0 Amortization of gain (loss) (26.9 ) (26.9 ) (64.9 ) 0.8 0.8 0.5 Amortization of prior service cost (0.7 ) (0.7 ) (0.7 ) (0.5 ) (0.5 ) — Other regulatory activity — — 6.1 — — — Total recognized in OCI or regulatory asset/liability 19.5 19.5 11.8 (5.5 ) (5.5 ) 3.5 Total recognized in net periodic benefit costs and OCI or regulatory asset/liability $ 89.5 $ 89.5 $ 77.1 $ (7.9 ) $ (7.9 ) $ 7.8 Pension Benefits Post-Retirement Benefits Year Ended December 31, 2016 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Components of net periodic benefit costs (millions) Service cost $ 25.3 $ 25.3 $ 42.0 $ 1.2 $ 1.2 $ 2.6 Interest cost 53.4 53.4 52.9 5.9 5.9 6.1 Expected return on plan assets (52.3 ) (52.3 ) (49.2 ) (6.9 ) (6.9 ) (3.0 ) Prior service cost 0.8 0.8 0.7 0.5 0.5 1.2 Recognized net actuarial (gain) loss 24.9 24.9 51.8 (1.1 ) (1.1 ) (1.5 ) Net periodic benefit costs before regulatory adjustment and intercompany allocations 52.1 52.1 98.2 (0.4 ) (0.4 ) 5.4 Regulatory adjustment 16.4 16.4 (3.1 ) (1.9 ) (1.9 ) 3.6 Intercompany allocations n/a — (36.0 ) n/a — (1.9 ) Net periodic benefit costs 68.5 68.5 59.1 (2.3 ) (2.3 ) 7.1 Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities Current year net (gain) loss 62.8 62.8 63.6 3.1 3.1 1.0 Amortization of gain (loss) (24.9 ) (24.9 ) (51.8 ) 1.1 1.1 1.5 Prior service cost (3.4 ) (3.4 ) — — — (10.1 ) Amortization of prior service cost (0.8 ) (0.8 ) (0.7 ) (0.5 ) (0.5 ) (1.2 ) Other regulatory activity — — (2.9 ) — — (1.9 ) Total recognized in OCI or regulatory asset/liability 33.7 33.7 8.2 3.7 3.7 (10.7 ) Total recognized in net periodic benefit costs and OCI or regulatory asset/liability $ 102.2 $ 102.2 $ 67.3 $ 1.4 $ 1.4 $ (3.6 ) For financial reporting purposes, the estimated prior service cost and net actuarial (gain) loss for the defined benefit plans are amortized from accumulated other comprehensive income (OCI) or a regulatory asset into net periodic benefit cost. The Evergy Companies amortize prior service cost on a straight-line basis over the average future service of the active employees (plan participants) benefiting under the plan at the time of the amendment. Evergy and Westar Energy amortize the net actuarial (gain) loss on a straight-line basis over the average future service of active plan participants benefiting under the plan without application of an amortization corridor. KCP&L amortizes the net actuarial (gain) loss on a rolling five-year average basis. The estimated amounts to be amortized in 2019 are detailed in the following table. Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (millions) Actuarial (gain) loss amortization $ 27.5 $ 25.4 $ 48.3 $ (1.2 ) $ (0.5 ) $ (1.5 ) Prior service cost amortization 1.9 1.7 0.9 0.5 0.5 — Pension and other post-retirement benefit plans with the PBO, ABO or accumulated other post-retirement benefit obligation (APBO) in excess of the fair value of plan assets at year-end are detailed in the following tables. KCP&L amounts are not included in consolidated Evergy as of December 31, 2017. December 31, 2018 Evergy Westar Energy KCP&L (millions) ABO for all defined benefit pension plans $ 2,257.9 $ 1,139.1 $ 1,096.7 Pension plans with the PBO in excess of plan assets Projected benefit obligation $ 2,553.4 $ 1,258.9 $ 1,272.4 Fair value of plan assets 1,603.4 804.6 798.8 Pension plans with the ABO in excess of plan assets Accumulated benefit obligation $ 2,257.9 $ 1,139.1 $ 1,096.7 Fair value of plan assets 1,603.4 804.6 798.8 Other post-retirement benefit plans with the APBO in excess of plan assets Accumulated other post-retirement benefit obligation $ 249.3 $ 133.6 $ 57.7 Fair value of plan assets 223.3 109.7 38.2 December 31, 2017 Evergy Westar Energy KCP&L (millions) ABO for all defined benefit pension plans $ 1,219.6 $ 1,219.6 $ 1,155.5 Pension plans with the PBO in excess of plan assets Projected benefit obligation $ 1,367.0 $ 1,367.0 $ 1,331.7 Fair value of plan assets 887.0 887.0 848.4 Pension plans with the ABO in excess of plan assets Accumulated benefit obligation $ 1,219.6 $ 1,219.6 $ 1,155.5 Fair value of plan assets 887.0 887.0 848.4 Other post-retirement benefit plans with the APBO in excess of plan assets Accumulated other post-retirement benefit obligation $ 138.6 $ 138.6 $ 111.6 Fair value of plan assets 124.1 124.1 81.5 The expected long-term rate of return on plan assets represents the Evergy Companies' estimate of the long-term return on plan assets and is based on historical and projected rates of return for current and planned asset classes in the plans' investment portfolios. Assumed projected rates of return for each asset class were selected after analyzing historical experience and future expectations of the returns of various asset classes. Based on the target asset allocation for each asset class, the overall expected rate of return for the portfolios was developed and adjusted for the effect of projected benefits paid from plan assets and future plan contributions. The following tables provide the weighted-average assumptions used to determine benefit obligations and net costs. KCP&L amounts are not included in consolidated Evergy as of December 31, 2017. Weighted-average assumptions used to determine the benefit obligation at December 31, 2018 Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Discount rate 4.35 % 4.35 % 4.36 % 4.33 % 4.33 % 4.33 % Rate of compensation increase 3.76 % 4.03 % 3.64 % 3.50 % n/a 3.50 % Weighted-average assumption used to determine the benefit obligation at December 31, 2017 Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Discount rate 3.73 % 3.73 % 3.72 % 3.67 % 3.67 % 3.64 % Rate of compensation increase 4.00 % 4.00 % 3.62 % 4.00 % 4.00 % 3.50 % Weighted-average assumptions used to determine net costs for the year ended December 31, 2018 Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Discount rate 3.73 % 3.73 % 3.72 % 3.67 % 3.73 % 3.64 % Expected long-term return on plan assets 6.52 % 6.67 % 6.46 % 6.00 % 6.00 % 2.80 % Rate of compensation increase 3.92 % 4.00 % 3.62 % 3.50 % n/a 3.50 % Weighted-average assumptions used to determine net costs for the year ended December 31, 2017 Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Discount rate 4.25 % 4.25 % 4.31 % 4.31 % 4.31 % 4.20 % Expected long-term return on plan assets 6.64 % 6.64 % 6.73 % 6.00 % 6.00 % 2.00 % Rate of compensation increase 4.00 % 4.00 % 3.62 % 4.00 % 4.00 % 3.50 % Evergy expects to contribute $115.5 million to the pension plans in 2019 to meet Employee Retirement Income Security Act of 1974, as amended (ERISA) funding requirements and regulatory orders, of which $37.0 million is expected to be paid by Westar Energy and $78.5 million is expected to be paid by KCP&L. The Evergy Companies' funding policy is to contribute amounts sufficient to meet the ERISA funding requirements and MPSC and KCC rate orders plus additional amounts as considered appropriate; therefore, actual contributions may differ from expected contributions. Also in 2019, Evergy expects to contribute $2.8 million to the post-retirement benefit plans, of which $0.7 million is expected to be paid by Westar Energy and $2.1 million is expected to be paid by KCP&L. The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid through 2028. Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (millions) 2019 $ 193.0 $ 96.7 $ 94.9 $ 20.3 $ 10.9 $ 9.4 2020 188.9 94.9 92.8 19.8 11.0 8.9 2021 189.4 95.3 92.8 20.6 11.3 9.3 2022 187.4 92.7 93.4 21.1 11.5 9.6 2023 186.1 90.0 94.7 21.5 11.7 9.8 2024-2028 928.7 432.7 488.3 110.7 58.5 52.1 Westar Energy and KCP&L each maintain separate trusts for both their qualified pension and post-retirement benefits. These plans are managed in accordance with prudent investor guidelines contained in the ERISA requirements. The primary objective of the Westar Energy pension plan is to provide a source of retirement income for its participants and beneficiaries, and the primary financial objective of the plan is to improve its funded status. The primary objective of the Westar Energy post-retirement benefit plan is growth in assets and the preservation of principal, while minimizing interim volatility, to meet anticipated claims of plan participants. The primary objective of the KCP&L pension plans is to earn the highest possible return on plan assets within a reasonable and prudent level of risk. The primary objective of the KCP&L post-retirement benefit plans is to preserve capital, maintain sufficient liquidity and earn a consistent rate of return. The investment strategies of both the Westar Energy and KCP&L pension and post-retirement plans support the above objectives of the plans. The portfolios are invested, and periodically rebalanced, to achieve the targeted allocations detailed below. The following table provides the target asset allocations by asset class for the Westar Energy and KCP&L pension and other post-retirement plan assets. Pension Benefits Post-Retirement Benefits Westar Energy KCP&L Westar Energy KCP&L Domestic equities 29 % 32 % 52 % 3 % International equities 20 % 21 % 13 % — % Bonds 36 % 36 % 35 % 85 % Mortgage & asset backed securities — % — % — % 4 % Real estate investments 4 % 6 % — % — % Other investments 11 % 5 % — % 8 % Fair Value Measurements Evergy classifies recurring and non-recurring fair value measurements based on the fair value hierarchy as discussed in Note 13. The following are descriptions of the valuation methods of the primary fair value measurements disclosed below. Domestic equities - consist of individually held domestic equity securities and domestic equity mutual funds. Securities and funds, which are publicly quoted, are valued based on quoted prices in active markets and are categorized as Level 1. Funds that are traded in less than active markets or priced with models using highly observable inputs are categorized as Level 2. Funds that are valued by fund administrators using the net asset value (NAV) per fund share, derived from the quoted prices in active markets of the underlying securities are not classified within the fair value hierarchy. International equities - consist of individually held international equity securities and international equity mutual funds. Securities and funds, which are publicly quoted, are valued based on quoted prices in active markets and are categorized as Level 1. Funds that are traded in less than active markets or priced with models using highly observable inputs are categorized as Level 2. Funds that are valued by fund administrators using the NAV per fund share, derived from the quoted prices in active markets of the underlying securities are not classified within the fair value hierarchy. Bond funds - consist of funds maintained by investment companies that invest in various types of fixed income securities consistent with the funds' stated objectives. Funds that are traded in less than active markets or are priced with models using highly observable inputs are categorized as Level 2 and funds that are valued by fund administrators using the NAV per fund share, derived from the quoted prices in active markets of the underlying securities, are not classified within the fair value hierarchy. Corporate bonds - consists of individually held, primarily domestic, corporate bonds that are traded in less than active markets or priced with models using highly observable inputs that are categorized as Level 2. U.S. Treasury and agency bonds - consists of individually held U.S. Treasury securities and U.S. agency bonds. U.S. Treasury securities, which are publicly quoted, are valued based on quoted prices in active markets and are categorized as a Level 1. U.S. agency bonds, which are publicly quoted, are traded in less than active markets or priced with models using highly observable inputs and are categorized as Level 2. Mortgage and asset backed securities - consists of individually held securities that are traded in less than active markets or valued with models using highly observable inputs that are categorized as Level 2. Real estate investments - consists of traded real estate investment trusts valued at the closing price reported on the major market on which the trusts are traded and are categorized as Level 1 and institutional trust funds valued at NAV per fund share and are not categorized in the fair value hierarchy. Combination debt/equity/other fund - consists of a fund that invests in various types of debt, equity and other asset classes consistent with the fund's stated objectives. The fund, which is publicly quoted, is valued based on quoted prices in active markets and is categorized as Level 1. Alternative investments - consists of investments in institutional trust and hedge funds that are valued by fund administrators using the NAV per fund share, derived from the underlying investments of the fund, and are not classified within the fair value hierarchy. Short-term investments - consists of fund investments in high-quality, short-term, U.S. dollar-denominated instruments with an average maturity of 60 days that are valued at NAV per fund share and are not categorized in the fair value hierarchy. Cash and cash equivalents - consists of investments with original maturities of three months or less when purchased that are traded in active markets and are categorized as Level 1. The fair values of the Evergy Companies' pension plan assets at December 31, 2018 and 2017 , by asset category are in the following tables. Fair Value Measurements Using Description December 31 Level 1 Level 2 Level 3 Assets measured at NAV (millions) Westar Energy Pension Plans Domestic equities $ 215.0 $ 144.7 $ — $ — $ 70.3 International equities 138.7 91.8 — — 46.9 Bond funds 296.4 255.4 — — 41.0 Real estate investments 44.8 — — — 44.8 Combination debt/equity/other fund 30.1 30.1 — — — Alternative investment funds 73.6 — — — 73.6 Short-term investments 6.0 — — — 6.0 Total $ 804.6 $ 522.0 $ — $ — $ 282.6 KCP&L Pension Plans Domestic equities $ 238.1 $ 198.6 $ — $ — $ 39.5 International equities 150.9 104.0 — — 46.9 Bond funds 67.4 19.3 — — 48.1 Corporate bonds 123.6 — 123.6 — — U.S. Treasury and agency bonds 69.9 52.4 17.5 — — Mortgage and asset backed securities 5.5 — 5.5 — — Real estate investments 48.2 12.6 — — 35.6 Combination debt/equity/other fund 13.5 13.5 — — — Alternative investment funds 31.6 — — — 31.6 Cash and cash equivalents 49.8 49.8 — — — Other 0.3 — 0.3 — — Total $ 798.8 $ 450.2 $ 146.9 $ — $ 201.7 Fair Value Measurements Using Description December 31 Level 1 Level 2 Level 3 Assets measured at NAV (millions) Westar Energy Pension Plans (a) Domestic equities $ 256.1 $ — $ 232.2 $ — $ 23.9 International equities 177.9 — 177.9 — — Bond funds 299.5 — 299.5 — — Real estate investments 41.8 — — — 41.8 Combination debt/equity/other fund 36.2 — 36.2 — — Alternative investment funds 70.3 — 17.0 — 53.3 Short-term investments 5.2 — 5.2 — — Total $ 887.0 $ — $ 768.0 $ — $ 119.0 KCP&L Pension Plans Domestic equities $ 263.9 $ 220.5 $ — $ — $ 43.4 International equities 176.0 123.5 — — 52.5 Bond funds 71.8 21.4 — — 50.4 Corporate bonds 125.8 — 125.8 — — U.S. Treasury and agency bonds 69.8 51.5 18.3 — — Mortgage and asset backed securities 5.9 — 5.9 — — Real estate investments 46.4 13.6 — — 32.8 Combination debt/equity/other fund 15.9 15.9 — — — Alternative investment funds 32.7 — — — 32.7 Cash and cash equivalents 35.6 35.6 — — — Other 4.6 — 4.6 — — Total $ 848.4 $ 482.0 $ 154.6 $ — $ 211.8 (a) In 2018, Evergy and Westar Energy re-evaluated the classification, within the fair value hierarchy, of their various fund investments within the Westar Energy Pension Plans. As a result, Evergy and Westar Energy determined that certain fund investments within the Westar Energy Pension Plans in the amount of $607.6 million as of December 31, 2017, should have been classified as Level 1, instead of Level 2. This determination is based on the fact that the fair value of these funds is based on daily published prices at which Evergy and Westar Energy are able to redeem their investments without restriction on a daily basis. Evergy and Westar Energy also determined that certain fund investments within the Westar Energy Pension Plans in the amount of $160.4 million as of December 31, 2017, should have been measured using the NAV per share (or its equivalent) practical expedient, instead of as a Level 2 investment. This determination is based on the fact that these funds do not meet the definition of readily determinable fair value due to the absence of a published NAV. Evergy and Westar Energy have determined that these errors are immaterial to their current and previously filed financial reports and accordingly, have not revised prior periods but have reflected the changes in fair value hierarchy classification as of December 31, 2018. The fair values of the Evergy Companies' post-retirement plan assets at December 31, 2018 and 2017 , by asset category are in the following tables. Fair Value Measurements Using Description December 31 Level 1 Level 2 Level 3 Assets measured at NAV (millions) Westar Energy Post-Retirement Benefit Plans Domestic equities $ 56.4 $ — $ — $ — $ 56.4 International equities 14.0 — — — 14.0 Bond funds 38.4 — — — 38.4 Short-term investments 0.7 — — — 0.7 Cash and cash equivalents 0.2 0.2 — — — Total $ 109.7 $ 0.2 $ — $ — $ 109.5 KCP&L Post-Retirement Benefit Plans Domestic equities $ 2.5 $ 2.5 $ — $ — $ — International equities 0.9 0.9 — — — Bond funds 75.0 0.2 — — 74.8 Corporate bonds 17.4 — 17.4 — — U.S. Treasury and agency bonds 10.3 2.6 7.7 — — Mortgage and asset backed securities 2.5 — 2.5 — — Cash and cash equivalents 4.7 4.7 — — — Other 0.3 — 0.3 — — Total $ 113.6 $ 10.9 $ 27.9 $ — $ 74.8 Fair Value Measurements Using Description December 31 Level 1 Level 2 Level 3 Assets measured at NAV (millions) Westar Energy Post-Retirement Benefit Plans (a) Domestic equities $ 65.2 $ — $ 65.2 $ — $ — International equities 16.2 — 16.2 — — Bond funds 42.1 — 42.1 — — Cash and cash equivalents 0.6 — 0.6 — — Total $ 124.1 $ — $ 124.1 $ — $ — KCP&L Post-Retirement Benefit Plans Domestic equities $ 3.7 $ 3.7 $ — $ — $ — Bond funds 56.6 0.2 — — 56.4 Corporate bonds 16.7 — 16.7 — — U.S. Treasury and agency bonds 8.5 3.0 5.5 — — Mortgage and asset backed securities 3.6 — 3.6 — — Cash and cash equivalents 25.3 25.3 — — — Other 1.4 — 1.4 — — Total $ 115.8 $ 32.2 $ 27.2 $ — $ 56.4 (a) In 2018, Evergy and Westar Energy re-evaluated the classification, within the fair value hierarchy, of their various fund investments within the Westar Energy Post-Retirement Benefit Plans. As a result, Evergy and Westar Energy determined that certain fund investments within the Westar Energy Post-Retirement Benefit Plans in the amount of $124.1 million as of December 31, 2017, should have been measured using the NAV per share (or its equivalent) practical expedient, instead of as a Level 2 investment. This determination is based on the fact that these funds do not meet the definition of readily determinable fair value due to the absence of a published NAV. Evergy and Westar Energy have determined that this error is immaterial to their current and previously filed financial reports and accordingly, have not revised prior periods but have reflected the changes in fair value hierarchy classification as of December 31, 2018. Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. The cost trend assumptions are detailed in the following table. Assumed annual health care cost growth rates as of December 31, 2018 Evergy Westar Energy KCP&L Health care cost trend rate assumed for next year 6.5 % 6.5 % 6.5 % Rate to which the cost trend is assumed to decline (the ultimate trend rate) 4.5 % 4.5 % 4.5 % Year that rate reaches ultimate trend 2027 2027 2027 Assumed annual health care cost growth rates as of December 31, 2017 Evergy Westar Energy KCP&L Health care cost trend rate assumed for next year 6.0 % 6.0 % 6.8 % Rate to which the cost trend is assumed to decline (the ultimate trend rate) 5.0 % 5.0 % 4.5 % Year that rate reaches ultimate trend 2020 2020 2027 The effects of a one-percentage point change in the assumed health care cost trend rates, holding all other assumptions constant, at December 31, 2018 , are detailed in the following table. Evergy Westar Energy (a) KCP&L Effect of 1% increase (millions) Effect on total service and interest component $ — $ — $ 0.1 Effect on post-retirement benefit obligation 0.2 (0.1 ) — Effect of 1% decrease Effect on total service and interest component $ — $ — $ 0.3 Effect on post-retirement benefit obligation (0.1 ) 0.1 (0.2 ) (a) Westar Energy includes only the effect of health care cost trend rates for Wolf Creek because the Westar Energy post-retirement benefit plan includes a fixed monthly stipend for health care and therefore is not affected by changes in health care costs. Employee Savings Plans Evergy has defined contribution savings plans (401(k)) that cover substantially all employees. Evergy matches employee contributions, subject to limits. The annual costs of the plans are detailed in the following table. KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018. 2018 2017 2016 (millions) Evergy $ 16.3 $ 9.7 $ 9.6 Westar Energy 9.9 9.7 9.6 KCP&L 8.3 7.7 8.0

Equity Compensation

Equity Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Compensation	10. EQUITY COMPENSATION Upon the consummation of the merger, Evergy assumed both Westar Energy's Long-Term Incentive and Share Award plan (LTISA) and Great Plains Energy's Amended Long-Term Incentive Plan, which was renamed the Evergy, Inc. Long-Term Incentive Plan. All outstanding share-based payment awards under Westar Energy's LTISA vested at the closing of the merger transaction and were converted into a right to receive Evergy common stock with the exception of certain RSUs and deferred director share units issued prior to the closing of the merger to certain directors, officers and employees of Westar Energy. The vesting of these shares resulted in the recognition of $14.6 million of compensation expense in Evergy's and Westar Energy's consolidated statements of income and comprehensive income for 2018 . All of Great Plains Energy's outstanding performance shares, restricted stock, RSUs and director deferred share units under Great Plains Energy's Amended Long-Term Incentive Plan were converted into equivalent Evergy performance shares, restricted stock, RSUs and director deferred share units at Great Plains Energy's merger exchange ratio of 0.5981 . The estimated fair value of these converted awards that was allocated to the purchase price was $12.5 million , after-tax. See Note 2 for more information regarding the merger. The following table summarizes the Evergy Companies' equity compensation expense and the associated income tax benefit. 2018 2017 2016 Evergy (millions) Equity compensation expense $ 30.7 $ 8.9 $ 9.2 Income tax benefit 1.4 3.5 3.7 Westar Energy Equity compensation expense $ 24.8 $ 8.9 $ 9.2 Income tax benefit 1.4 3.5 3.7 KCP&L (a) Equity compensation expense $ 6.5 $ 4.2 $ 3.2 Income tax benefit 0.1 1.6 1.0 (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018 . Performance Shares The vesting of performance shares is contingent upon achievement of specific performance goals over a stated period of time as approved by the Compensation and Leadership Development Committee of the Evergy Board. The number of performance shares ultimately vested can vary from the number of shares initially granted depending on either Great Plains Energy's performance prior to the closing of the merger transaction or Evergy's performance based on the stated performance period of the awards. Compensation expense for performance shares is calculated by recognizing the portion of the grant date fair value for each reporting period for which the requisite service has been rendered. Dividends are accrued over the vesting period and paid in cash based on the number of performance shares ultimately paid. The fair value of the converted Great Plains Energy performance share awards was estimated using the market value of Westar Energy's and Great Plains Energy's common stock at the valuation date and a Monte Carlo simulation technique that incorporates assumptions for inputs of expected volatilities, dividend yield and risk-free rates. Expected volatility is based on daily stock price change based on historical common stock information during a historical period commensurate with the remaining term of the performance period of the grant. The risk-free rate is based upon the rate at the time of the evaluation for zero-coupon government bonds with a maturity consistent with the remaining performance period of the grant. The dividend yield is based on the most recent dividends paid by Westar Energy, as Evergy's stock price assumes Westar Energy's stock price on a forward basis, and the grant date stock price on the valuation date. For the Great Plains Energy performance shares converted into Evergy awards upon the closing of the merger, inputs for expected volatility, dividend yield, and risk-free rates were 16.6% - 18.5% , 2.96% and 1.8% - 2.6% , respectively. Evergy and Westar Energy did not have any performance share awards issued and outstanding prior to the close of the merger. Performance share activity for 2018 is summarized in the following table. Performance Shares Grant Date Fair Value* Beginning balance January 1, 2018 — $ — Converted Great Plains Energy awards upon merger 351,708 63.79 Forfeited (3,212 ) 63.44 Ending balance December 31, 2018 348,496 63.80 * weighted-average At December 31, 2018 , the remaining weighted-average contractual term was 1.0 years. The weighted-average grant-date fair value of shares granted in 2018 was $63.79 . At December 31, 2018 , there was $6.6 million of total unrecognized compensation expense, net of forfeiture rates, related to converted Great Plains Energy performance shares granted under its Amended Long-Term Incentive Plan, which will be recognized over the remaining weighted-average contractual term. Restricted Stock Restricted stock cannot be sold or otherwise transferred by the recipient prior to vesting and has a value equal to the fair market value of the shares on the issue date. Restricted stock shares vest over a stated period of time with accruing reinvested dividends subject to the same restrictions. Compensation expense, calculated by multiplying shares by the grant-date fair value related to restricted stock, is recognized on a straight-line basis over the requisite service period of the award. Evergy and Westar Energy did not have any restricted stock awards issued and outstanding prior to the close of the merger. Restricted stock activity for 2018 is summarized in the following table. Nonvested Restricted Stock Grant Date Fair Value* Beginning balance January 1, 2018 — $ — Converted Great Plains Energy awards upon merger 122,505 54.05 Vested (4,760 ) 54.50 Forfeited (1,070 ) 54.04 Ending balance December 31, 2018 116,675 54.03 * weighted-average At December 31, 2018 , the remaining weighted-average contractual term was 1.2 years. The weighted-average grant-date fair value of shares granted in 2018 was $54.05 . At December 31, 2018 , there was $2.6 million of total unrecognized compensation expense, net of forfeiture rates, related to converted Great Plains Energy restricted stock granted under its Amended Long-Term Incentive Plan, which will be recognized over the remaining weighted-average contractual term. The total fair value of shares vested was $0.3 million for 2018. Restricted Share Units Evergy and Westar Energy have historically used RSUs for their stock-based compensation awards. RSU awards are grants that entitle the holder to receive shares of common stock as the awards vest. These RSU awards are defined as nonvested shares and do not include restrictions once the awards have vested. These RSUs have either taken the form of RSUs with only service requirements that vest solely upon the passage of time or RSUs with performance measures that vest upon expiration of the award term. All issued and outstanding Evergy and Westar Energy RSU awards with performance measures vested in connection with the closing of the merger transaction in June 2018. Evergy measures the fair value of RSUs with only service requirements based on the fair market value of the underlying common stock as of the grant date. RSU awards with only service conditions recognize compensation expense by multiplying shares by the grant-date fair value related to the RSU and recognizing it on a straight-line basis over the requisite service period for the entire award, including for those RSUs that have a graded vesting schedule. Nonforfeitable dividend equivalents, or the rights to receive cash equal to the value of dividends paid on Evergy's common stock, are paid on certain of these RSUs during the vesting period. Nonforfeitable dividend equivalents are recorded directly to retained earnings. RSU activity for awards with only service requirements for 2018 is summarized in the following table. Nonvested Restricted Share Units Grant Date Fair Value* Beginning balance January 1, 2018 255,964 $ 46.09 Granted 222,465 52.16 Converted Great Plains Energy awards upon merger 82,331 53.77 Vested (342,599 ) 46.81 Forfeited (905 ) 50.73 Ending balance December 31, 2018 217,256 54.07 * weighted-average At December 31, 2018 , the remaining weighted-average contractual term related to RSU awards with only service requirements was 1.4 years. The weighted-average grant-date fair value of RSUs granted with only service requirements was $52.16 , $53.25 and $46.35 in 2018, 2017 and 2016, respectively. At December 31, 2018 , there was $7.8 million of unrecognized compensation expense related to unvested RSUs. The total fair value of RSUs with only service requirements that vested was $16.0 million , $6.1 million and $5.2 million in 2018, 2017 and 2016, respectively.

Short-term Borrowings and Short

Short-term Borrowings and Short-term Bank Lines of Credit	12 Months Ended
	Dec. 31, 2018
Short-term Borrowings and Short-term Bank Lines of Credit [Abstract]
Short-term Borrowings and Short-term Bank Lines of Credit	11 . SHORT-TERM BORROWINGS AND SHORT-TERM BANK LINES OF CREDIT In September 2018, Evergy entered into a $2.5 billion master credit facility, which expires in 2023 . Evergy, Westar Energy, KCP&L and GMO have borrowing capacity under the master credit facility with specific sublimits for each borrower. These sublimits can be unilaterally adjusted by Evergy for each borrower provided the sublimits remain within minimum and maximum sublimits as specified in the facility. A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times. As of December 31, 2018 , Evergy, Westar Energy, KCP&L and GMO were in compliance with this covenant. In connection with the entry into the master credit facility, each of Evergy (as successor to Great Plains Energy), Westar Energy, KCP&L and GMO terminated its existing credit facilities in September 2018. The following table summarizes the committed credit facilities (excluding receivable sale facilities discussed in Note 4) available to the Evergy Companies as of December 31, 2018 and 2017 . Amounts Drawn Credit Facility Commercial Paper Letters of Credit Cash Borrowings Available Borrowings Weighted Average Interest Rate on Short-Term Borrowings December 31, 2018 (millions) Evergy, Inc. $ 450.0 n/a $ 1.0 $ — $ 449.0 —% Westar Energy 1,000.0 411.7 18.3 — 570.0 3.08% KCP&L 600.0 176.9 2.7 — 420.4 2.95% GMO 450.0 150.0 2.1 — 297.9 3.00% Evergy $ 2,500.0 $ 738.6 $ 24.1 $ — $ 1,737.3 December 31, 2017 Westar Energy (b) $ 979.3 $ 275.7 $ 11.8 $ — $ 691.8 1.83% KCP&L (a) 600.0 167.5 2.7 — 429.8 1.95% Evergy 979.3 275.7 11.8 — 691.8 1.83% (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017 . (b) $20.7 million of Westar Energy's $730.0 million and $270.0 million revolving credit facilities expired in September 2017.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Long-Term Debt	12 . LONG-TERM DEBT The Evergy Companies' long-term debt is detailed in the following tables. December 31, 2018 Issuing Entity Year Due Evergy Westar Energy KCP&L Mortgage Bonds (millions) 5.10% Series Westar Energy, Inc. 2020 $ 250.0 $ 250.0 $ — 3.25% Series Westar Energy, Inc. 2025 250.0 250.0 — 2.55% Series Westar Energy, Inc. 2026 350.0 350.0 — 3.10% Series Westar Energy, Inc. 2027 300.0 300.0 — 4.125% Series Westar Energy, Inc. 2042 550.0 550.0 — 4.10% Series Westar Energy, Inc. 2043 430.0 430.0 — 4.625% Series Westar Energy, Inc. 2043 250.0 250.0 — 4.25% Series Westar Energy, Inc. 2045 300.0 300.0 — 6.70% Series KGE 2019 300.0 300.0 — 6.15% Series KGE 2023 50.0 50.0 — 6.53% Series KGE 2037 175.0 175.0 — 6.64% Series KGE 2038 100.0 100.0 — 4.30% Series KGE 2044 250.0 250.0 — 2.95% EIRR bonds KCP&L 2023 79.5 — 79.5 7.15% Series 2009A (8.59% rate) (a) KCP&L 2019 400.0 — 400.0 9.44% Series GMO 2019-2021 3.4 — — Pollution Control Bonds 2.46% Series (b) Westar Energy, Inc. 2032 45.0 45.0 — 2.46% Series (b) Westar Energy, Inc. 2032 30.5 30.5 — 2.46% Series (b) KGE 2027 21.9 21.9 — 2.50% Series KGE 2031 50.0 50.0 — 2.46% Series (b) KGE 2032 14.5 14.5 — 2.46% Series (b) KGE 2032 10.0 10.0 — 1.865% Series 2007A and 2007B (b) KCP&L 2035 146.5 — 146.5 2.75% Series 2008 KCP&L 2038 23.4 — 23.4 Senior Notes 3.15% Series KCP&L 2023 300.0 — 300.0 3.65% Series KCP&L 2025 350.0 — 350.0 6.05% Series (5.78% rate) (a) KCP&L 2035 250.0 — 250.0 5.30% Series KCP&L 2041 400.0 — 400.0 4.20% Series KCP&L 2047 300.0 — 300.0 4.20% Series KCP&L 2048 300.0 — 300.0 8.27% Series GMO 2021 80.9 — — 3.49% Series A GMO 2025 36.0 — — 4.06% Series B GMO 2033 60.0 — — 4.74% Series C GMO 2043 150.0 — — 4.85% Series Evergy, Inc. (g) 2021 350.0 — — 5.292% Series Evergy, Inc. (g) 2022 287.5 — — Medium Term Notes 7.33% Series GMO 2023 3.0 — — 7.17% Series GMO 2023 7.0 — — Fair value adjustment (f) 144.8 — — Current maturities (c) (705.4 ) (300.0 ) (400.0 ) Unamortized debt discount and debt issuance costs (57.2 ) (37.1 ) (19.3 ) Total excluding current maturities (d) $ 6,636.3 $ 3,389.8 $ 2,130.1 December 31, 2017 Issuing Entity Year Due Evergy Westar Energy KCP&L (e) Mortgage Bonds (millions) 5.10% Series Westar Energy, Inc. 2020 $ 250.0 $ 250.0 $ — 3.25% Series Westar Energy, Inc. 2025 250.0 250.0 — 2.55% Series Westar Energy, Inc. 2026 350.0 350.0 — 3.10% Series Westar Energy, Inc. 2027 300.0 300.0 — 4.125% Series Westar Energy, Inc. 2042 550.0 550.0 — 4.10% Series Westar Energy, Inc. 2043 430.0 430.0 — 4.625% Series Westar Energy, Inc. 2043 250.0 250.0 — 4.25% Series Westar Energy, Inc. 2045 300.0 300.0 — 6.70% Series KGE 2019 300.0 300.0 — 6.15% Series KGE 2023 50.0 50.0 — 6.53% Series KGE 2037 175.0 175.0 — 6.64% Series KGE 2038 100.0 100.0 — 4.30% Series KGE 2044 250.0 250.0 — 2.95% EIRR bonds KCP&L 2023 — — 79.5 7.15% Series 2009A (8.59% rate) (a) KCP&L 2019 — — 400.0 Pollution Control Bonds 1.92% Series (b) Westar Energy, Inc. 2032 45.0 45.0 — 1.94% Series (b) Westar Energy, Inc. 2032 30.5 30.5 — 2.00% Series (b) KGE 2027 21.9 21.9 — 2.50% Series KGE 2031 50.0 50.0 — 2.00% Series (b) KGE 2032 14.5 14.5 — 2.00% Series (b) KGE 2032 10.0 10.0 — 1.329% Series 2007A and 2007B (b) KCP&L 2035 — — 146.5 2.875% Series 2008 KCP&L 2038 — — 23.4 Senior Notes 6.375% Series (7.49% rate) (a) KCP&L 2018 — — 350.0 3.15% Series KCP&L 2023 — — 300.0 3.65% Series KCP&L 2025 — — 350.0 6.05% Series (5.78% rate) (a) KCP&L 2035 — — 250.0 5.30% Series KCP&L 2041 — — 400.0 4.20% Series KCP&L 2047 — — 300.0 Current maturities — — (350.0 ) Unamortized debt discount and debt issuance costs (39.3 ) (39.3 ) (17.2 ) Total excluding current maturities (d) $ 3,687.6 $ 3,687.6 $ 2,232.2 (a) Rate after amortizing gains/losses recognized in other comprehensive income (OCI) on settlements of interest rate hedging instruments. (b) Variable rate. (c) Evergy's current maturities total as of December 31, 2018 , includes $4.3 million of fair value adjustments recorded in connection with purchase accounting for the merger transaction. (d) At December 31, 2018 and 2017 , does not include $50.0 million and $21.9 million of secured Series 2005 Environmental Improvement Revenue Refunding (EIRR) bonds because the bonds were repurchased in September 2015 and are held by KCP&L. (e) KCP&L amounts are not included in consolidated Evergy at December 31, 2017. (f) Represents the fair value adjustments recorded at Evergy consolidated related to the long-term debt of Great Plains Energy, KCP&L and GMO in connection with purchase accounting for the merger transaction. This amount is not part of future principal payments and will amortize over the remaining life of the associated debt instruments. (g) Originally issued by Great Plains Energy but assumed by Evergy, Inc. as part of the merger transaction. The following table summarizes Evergy's and Westar Energy's long-term debt of VIEs. December 31 2018 2017 (millions) 2.398% due 2021 $ 81.4 $ 109.9 Current maturities (30.3 ) (28.5 ) Total excluding current maturities $ 51.1 $ 81.4 Mortgage Bonds The Westar Energy and KGE mortgages each contain provisions restricting the amount of first mortgage bonds (FMBs) that could be issued by each entity. Westar Energy and KGE must be in compliance with such restrictions prior to the issuance of additional first mortgage bonds or other secured indebtedness. The amount of Westar Energy FMBs authorized by its Mortgage and Deed of Trust, dated July 1, 1939, as supplemented, is subject to certain limitations as described below. The amount of KGE FMBs authorized by the KGE Mortgage and Deed of Trust, dated April 1, 1940, as supplemented and amended, is limited to a maximum of $3.5 billion , unless amended further. FMBs are secured by utility assets. Amounts of additional FMBs that may be issued are subject to property, earnings and certain restrictive provisions, except in connection with certain refundings, of each mortgage. As of December 31, 2018 , approximately $344.5 million principal amount of additional Westar Energy FMBs could be issued under the most restrictive provisions in Westar Energy's mortgage. As of December 31, 2018 , KGE had sufficient capacity under the most restrictive provisions in the mortgage to meet its near term financing and refinancing needs. KCP&L has issued mortgage bonds under the General Mortgage Indenture and Deed of Trust dated as of December 1, 1986, as supplemented, which creates a mortgage lien on substantially all of KCP&L's utility plant. Additional KCP&L mortgage bonds may be issued on the basis of property additions or retired bonds. As of December 31, 2018, KCP&L had sufficient capacity under the most restrictive provisions in the mortgage to meet its near term financing and refinancing needs. GMO has issued mortgage bonds under the General Mortgage Indenture and Deed of Trust dated April 1, 1946, as supplemented, which creates a mortgage lien on a portion of GMO's utility plant. Pollution Control Bonds In July 2018, KCP&L remarketed its unsecured Series 2008 EIRR bonds maturing in 2038 totaling $23.4 million at a fixed rate of 2.75% through June 30, 2022. In December 2018, KCP&L remarketed its unsecured Series 2007A and 2007B EIRR bonds maturing in 2035 totaling $146.5 million at a variable rate that will be determined weekly. In December 2018, Westar Energy, Inc. remarketed its Series 1994 pollution control bonds maturing in 2032 totaling $45.0 million and $30.5 million , collateralized by Westar Energy FMBs, at variable rates that will be determined weekly. In December 2018, KGE remarketed the following series of pollution control bonds, which are collateralized by KGE FMBs: • Series 1994 maturing in 2032 totaling $14.5 million and $10.0 million at variable rates that will be determined weekly; and • Series 1994B maturing in 2027 totaling $21.9 million at a variable rate that will be determined weekly. Senior Notes Under the terms of the note purchase agreement for GMO's Series A, B and C Senior Notes, GMO is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the agreement, not greater than 0.65 to 1.00. In addition, GMO's priority debt, as defined in the agreement, cannot exceed 15% of consolidated tangible net worth, as defined in the agreement. At December 31, 2018, GMO was in compliance with these covenants. In March 2018, KCP&L issued, at a discount, $300.0 million of 4.20% unsecured Senior Notes, maturing in 2048 . KCP&L also repaid its $350.0 million of 6.375% unsecured Senior Notes at maturity in March 2018. As a result of the consummation of the merger transaction, a change in control provision in GMO's Series A, B and C Senior Notes was triggered that allowed holders a one-time option to elect for early repayment of their notes at par value, plus accrued interest. Several holders of GMO's Series A and B Senior Notes elected this option and in July 2018, GMO redeemed $89.0 million of its Series A Senior Notes and $15.0 million of its Series B Senior Notes. Scheduled Maturities Evergy's, Westar Energy's and KCP&L's long-term debt maturities and the long-term debt maturities of VIEs for the next five years are detailed in the following table. 2019 2020 2021 2022 2023 (millions) Evergy (a) $ 701.1 $ 251.1 $ 432.0 $ 287.5 $ 439.5 Westar Energy (a) 300.0 250.0 — — 50.0 KCP&L 400.0 — — — 379.5 VIEs 30.3 32.3 18.8 — — (a) Excludes long-term debt maturities of VIEs.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	13 . FAIR VALUE MEASUREMENTS Values of Financial Instruments GAAP establishes a hierarchical framework for disclosing the transparency of the inputs utilized in measuring assets and liabilities at fair value. Management's assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the classification of assets and liabilities within the fair value hierarchy levels. In addition, the Evergy Companies measure certain investments that do not have a readily determinable fair value at NAV, which are not included in the fair value hierarchy. Further explanation of these levels and NAV is summarized below. Level 1 – Quoted prices are available in active markets for identical assets or liabilities. The types of assets and liabilities included in Level 1 are highly liquid and actively traded instruments with quoted prices, such as equities listed on public exchanges. Level 2 – Pricing inputs are not quoted prices in active markets, but are either directly or indirectly observable. The types of assets and liabilities included in Level 2 are certain marketable debt securities, financial instruments traded in less than active markets or other financial instruments priced with models using highly observable inputs. Level 3 – Significant inputs to pricing have little or no transparency. The types of assets and liabilities included in Level 3 are those with inputs requiring significant management judgment or estimation. NAV - Investments that do not have a readily determinable fair value are measured at NAV. These investments do not consider the observability of inputs and, therefore, they are not included within the fair value hierarchy. The Evergy Companies include in this category investments in private equity, real estate and alternative investment funds that do not have a readily determinable fair value. The underlying alternative investments include collateralized debt obligations, mezzanine debt and a variety of other investments. The Evergy Companies record cash and cash equivalents, accounts receivable and short-term borrowings on their consolidated balance sheets at cost, which approximates fair value due to the short-term nature of these instruments. Interest Rate Derivatives The Evergy Companies are exposed to market risks arising from changes in interest rates and may use derivative instruments to manage these risks. From time to time, this may include entering into interest rate swap agreements to protect against unfavorable interest rate changes relating to forecasted debt transactions. These interest rate swap agreements can be designated as cash flow hedges, in which case, gains and losses on the interest rate swaps are deferred in other comprehensive income to be recognized as an adjustment to interest expense over the same period that the hedged interest payments affect earnings. In December 2018, Evergy entered into an interest rate swap agreement with a notional amount of $500.0 million that has been designated as a cash flow hedge of a forecasted debt issuance in 2019. As of December 31, 2018, the interest rate swap had a fair value of $5.4 million and was recorded within other current liabilities on Evergy's consolidated balance sheet. For 2018, Evergy recorded a corresponding $5.4 million pre-tax loss in other comprehensive loss on Evergy's consolidated statements of comprehensive income. Fair Value of Long-Term Debt The Evergy Companies measure the fair value of long-term debt using Level 2 measurements available as of the measurement date. The book value and fair value of the Evergy Companies' long-term debt and long-term debt of variable interest entities is summarized in the following table. December 31 2018 2017 Book Value Fair Value Book Value Fair Value Long-term debt (a) (millions) Evergy (b) $ 7,341.7 $ 7,412.1 $ 3,687.6 $ 4,010.6 Westar Energy 3,689.8 3,771.3 3,687.6 4,010.6 KCP&L (c) 2,530.1 2,637.5 2,582.2 2,799.1 Long-term debt of variable interest entities (a) Evergy $ 81.4 $ 81.3 $ 109.9 $ 110.8 Westar Energy 81.4 81.3 109.9 110.8 (a) Includes current maturities. (b) Book value as of December 31, 2018 , includes $144.8 million of fair value adjustments recorded in connection with purchase accounting for the Great Plains Energy and Westar Energy merger, which are not part of future principal payments and will amortize over the remaining life of the associated debt instrument. See Note 2 for more information regarding the merger transaction. (c) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017. Recurring Fair Value Measurements The following tables include the Evergy Companies' balances of financial assets and liabilities measured at fair value on a recurring basis. Description December 31, 2018 Level 1 Level 2 Level 3 NAV Westar Energy (millions) Assets Nuclear decommissioning trust (a) Domestic equity funds $ 70.6 $ 63.9 $ — $ — $ 6.7 International equity funds 36.2 36.2 — — — Core bond fund 37.5 37.5 — — — High-yield bond fund 18.9 18.9 — — — Emerging markets bond fund 15.4 15.4 — — — Combination debt/equity/other fund 12.9 12.9 — — — Alternative investments fund 24.1 — — — 24.1 Real estate securities fund 11.8 — — — 11.8 Cash equivalents 0.1 0.1 — — — Total nuclear decommissioning trust 227.5 184.9 — — 42.6 Rabbi trust Core bond fund 24.8 — — — 24.8 Combination debt/equity/other fund 5.6 — — — 5.6 Cash equivalents 0.2 0.2 — — — Total rabbi trust 30.6 0.2 — — 30.4 Total $ 258.1 $ 185.1 $ — $ — $ 73.0 KCP&L Assets Nuclear decommissioning trust (a) Equity securities $ 166.6 $ 166.6 $ — $ — $ — Debt securities U.S. Treasury 42.1 42.1 — — — U.S. Agency 0.4 — 0.4 — — State and local obligations 2.1 — 2.1 — — Corporate bonds 30.9 — 30.9 — — Foreign governments 0.1 — 0.1 — — Cash equivalents 1.7 1.7 — — — Other 0.7 0.7 — — — Total nuclear decommissioning trust 244.6 211.1 33.5 — — Self-insured health plan trust (b) Equity securities 0.5 0.5 — — — Debt securities 3.9 0.3 3.6 — — Cash and cash equivalents 8.0 8.0 — — — Total self-insured health plan trust 12.4 8.8 3.6 — — Total $ 257.0 $ 219.9 $ 37.1 $ — $ — Other Evergy Assets Rabbi trusts Fixed income fund $ 13.2 $ — $ — $ — $ 13.2 Total rabbi trusts $ 13.2 $ — $ — $ — $ 13.2 Liabilities Interest rate swaps (e) $ 5.4 $ — $ 5.4 $ — $ — Total $ 5.4 $ — $ 5.4 $ — $ — Evergy Assets Nuclear decommissioning trust (a) $ 472.1 $ 396.0 $ 33.5 $ — $ 42.6 Rabbi trusts 43.8 0.2 — — 43.6 Self-insured health plan trust (b) 12.4 8.8 3.6 — — Total $ 528.3 $ 405.0 $ 37.1 $ — $ 86.2 Liabilities Interest rate swaps (e) $ 5.4 $ — $ 5.4 $ — $ — Total $ 5.4 $ — $ 5.4 $ — $ — Description December 31, 2017 Level 1 Level 2 Level 3 NAV Westar Energy (millions) Assets Nuclear decommissioning trust (a)(c) Domestic equity funds $ 73.8 $ — $ 68.7 $ — $ 5.1 International equity funds 47.9 — 47.9 — — Core bond fund 33.3 — 33.3 — — High-yield bond fund 18.1 — 18.1 — — Emerging markets bond fund 17.3 — 17.3 — — Combination debt/equity/other fund 14.1 — 14.1 — — Alternative investments fund 21.7 — — — 21.7 Real estate securities fund 10.8 — — — 10.8 Cash equivalents 0.1 0.1 — — — Total nuclear decommissioning trust 237.1 0.1 199.4 — 37.6 Rabbi trust (c) Core bond fund 27.3 — 27.3 — — Combination debt/equity/other fund 6.8 — 6.8 — — Cash equivalents 0.2 0.2 — — — Total rabbi trust 34.3 0.2 34.1 — — Total $ 271.4 $ 0.3 $ 233.5 $ — $ 37.6 KCP&L (d) Assets Nuclear decommissioning trust (a) Equity securities $ 183.8 $ 183.8 $ — $ — $ — Debt securities U.S. Treasury 35.3 35.3 — — — U.S. Agency 0.4 — 0.4 — — State and local obligations 2.1 — 2.1 — — Corporate bonds 34.1 — 34.1 — — Foreign governments 0.1 — 0.1 — — Cash equivalents 2.5 2.5 — — — Other 0.1 0.1 — — — Total nuclear decommissioning trust 258.4 221.7 36.7 — — Self-insured health plan trust (b) Equity securities 0.5 0.5 — — — Debt securities 2.7 0.3 2.4 — — Cash and cash equivalents 7.7 7.7 — — — Total self-insured health plan trust 10.9 8.5 2.4 — — Total $ 269.3 $ 230.2 $ 39.1 $ — $ — Evergy Assets Nuclear decommissioning trust (a)(c) $ 237.1 $ 0.1 $ 199.4 $ — $ 37.6 Rabbi trust (c) 34.3 0.2 34.1 — — Total $ 271.4 $ 0.3 $ 233.5 $ — $ 37.6 (a) Fair value is based on quoted market prices of the investments held by the trust and/or valuation models. (b) Fair value is based on quoted market prices of the investments held by the trust. Debt securities classified as Level 1 are comprised of U.S. Treasury securities. Debt securities classified as Level 2 are comprised of corporate bonds, U.S. Agency, state and local obligations, and other asset-backed securities. (c) In the second quarter of 2018, Evergy and Westar Energy re-evaluated the classification, within the fair value hierarchy, of their various fund investments within both Westar Energy's nuclear decommissioning trust and rabbi trusts. As a result, Evergy and Westar Energy determined that certain fund investments within the nuclear decommissioning trust in the amount of $199.4 million as of December 31, 2017, should have been classified as Level 1, instead of Level 2. This determination is based on the fact that the fair value of these funds is based on daily published prices at which Evergy and Westar Energy are able to redeem their investments without restriction on a daily basis. Evergy and Westar Energy also determined that certain fund investments within their rabbi trusts in the amount of $34.1 million as of December 31, 2017, should have been measured using the NAV per share (or its equivalent) practical expedient, instead of as a Level 2 investment. This determination is based on the fact that these funds do not meet the definition of readily determinable fair value due to the absence of a published NAV. Evergy and Westar Energy have determined that these errors are immaterial to their current and previously filed financial reports and accordingly, have not revised prior periods but have reflected the changes in fair value hierarchy classification as of December 31, 2018. (d) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017. (e) The fair value of interest rate swaps are determined by calculating the net present value of expected payments and receipts under the interest rate swaps using observable market inputs including interest rates and LIBOR swap rates. Certain Evergy and Westar Energy investments included in the table above are measured at NAV as they do not have readily determinable fair values. In certain situations, these investments may have redemption restrictions. The following table provides additional information on these Evergy and Westar Energy investments. December 31, 2018 December 31, 2017 December 31, 2018 Fair Unfunded Fair Unfunded Redemption Length of Value Commitments Value Commitments Frequency Settlement Westar Energy (millions) Nuclear decommissioning trust: Domestic equity funds $ 6.7 $ 4.3 $ 5.1 $ 2.8 (a) (a) Alternative investments fund (b) 24.1 — 21.7 — Quarterly 65 days Real estate securities fund (b) 11.8 — 10.8 — Quarterly 65 days Total $ 42.6 $ 4.3 $ 37.6 $ 2.8 Rabbi trust: Core bond fund $ 24.8 $ — $ — $ — (c) (c) Combination debt/equity/other fund 5.6 — — — (c) (c) Total $ 30.4 $ — $ — $ — Other Evergy Rabbi trusts: Fixed income fund (d) $ 13.2 $ — $ — $ — (c) (c) Total Evergy investments at NAV $ 86.2 $ 4.3 $ 37.6 $ 2.8 (a) This investment is in five long-term private equity funds that do not permit early withdrawal. Investments in these funds cannot be distributed until the underlying investments have been liquidated, which may take years from the date of initial liquidation. Three funds have begun to make distributions. The initial investment in the fourth and fifth fund occurred in the second quarter of 2016 and first quarter of 2018, respectively. The fourth fund's term is 15 years , subject to the general partner's right to extend the term for up to three additional one -year periods. The fifth fund's term will be 15 years after the initial closing date, subject to additional extensions approved by the Advisory Committee to provide for an orderly liquidation of fund investments and dissolution of the fund. (b) There is a holdback on final redemptions. (c) This investment can be redeemed immediately and is not subject to any restrictions on redemptions. (d) This investment is recorded at GMO. GMO amounts are not included in consolidated Evergy as of December 31, 2017. The Evergy Companies hold equity and debt investments classified as securities in various trusts including for the purposes of funding the decommissioning of Wolf Creek and for the benefit of certain retired executive officers of Westar Energy. The Evergy Companies record net realized and unrealized gains and losses on the nuclear decommissioning trusts in regulatory liabilities on their consolidated balance sheets and record net realized and unrealized gains and losses on Westar Energy's rabbi trust in the consolidated statements of income and comprehensive income. The following table summarizes the net unrealized gains (losses) for the Evergy Companies' nuclear decommissioning trusts and rabbi trusts. 2018 2017 2016 Westar Energy (millions) Nuclear decommissioning trust - equity securities $ (31.8 ) $ 15.7 $ 9.0 Rabbi trust 1.0 (14.3 ) 1.4 Total $ (30.8 ) $ 1.4 $ 10.4 KCP&L (a) Nuclear decommissioning trust - equity securities $ (20.7 ) $ 26.7 $ 14.8 Nuclear decommissioning trust - debt securities (2.5 ) 0.5 (0.3 ) Total $ (23.2 ) $ 27.2 $ 14.5 Evergy Nuclear decommissioning trust - equity securities $ (54.1 ) $ 15.7 $ 9.0 Nuclear decommissioning trust - debt securities (0.5 ) — — Rabbi trusts 1.0 (14.3 ) 1.4 Total $ (53.6 ) $ 1.4 $ 10.4 (a) KCP&L amounts are only included in consolidated Evergy from the date of the merger, June 4, 2018 through December 31, 2018 .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	14 . COMMITMENTS AND CONTINGENCIES Environmental Matters Set forth below are descriptions of contingencies related to environmental matters that may impact the Evergy Companies' operations or their financial results. Management's assessment of these contingencies, which are based on federal and state statutes and regulations, and regulatory agency and judicial interpretations and actions, has evolved over time. There are a variety of final and proposed laws and regulations that could have a material adverse effect on the Evergy Companies operations and consolidated financial results. Due in part to the complex nature of environmental laws and regulations, the Evergy Companies are unable to assess the impact of potential changes that may develop with respect to the environmental contingencies described below. Cross-State Air Pollution Update Rule In September 2016, the Environmental Protection Agency (EPA) finalized the Cross-State Air Pollution Update Rule (CSAPR). The final rule addresses interstate transport of nitrogen oxides emissions in 22 states including Kansas, Missouri and Oklahoma during the ozone season and the impact from the formation of ozone on downwind states with respect to the 2008 ozone National Ambient Air Quality Standards (NAAQS). Starting with the 2017 ozone season, the final rule revised the existing ozone season allowance budgets for Missouri and Oklahoma and established an ozone season budget for Kansas. In December 2018, the EPA finalized the CSAPR Close-Out Rule, which determined that the existing CSAPR Update Rule fully addresses applicable states' interstate pollution transport obligations for the 2008 ozone NAAQS. Therefore, the EPA is proposing no additional reduction in the current ozone season allowance budgets in order to address obligations for the 2008 ozone NAAQS. Various states and others are challenging the rule in the U.S. Court of Appeals for the D.C. Circuit (D.C. Circuit), but the rule remains in effect. It is not expected that this rule will have a material impact on the Evergy Companies' operations and consolidated financial results. National Ambient Air Quality Standards Under the Clean Air Act Amendments of 1990 (CAA), the EPA set NAAQS for certain emissions known as the "criteria pollutants" considered harmful to public health and the environment, including two classes of particulate matter (PM), ozone, nitrogen dioxide (NO 2 ) (a precursor to ozone), carbon monoxide and sulfur dioxide (SO 2 ), which result from fossil fuel combustion. Areas meeting the NAAQS are designated attainment areas while those that do not meet the NAAQS are considered nonattainment areas. Each state must develop a plan to bring nonattainment areas into compliance with the NAAQS. NAAQS must be reviewed by the EPA at five -year intervals. In October 2015, the EPA strengthened the ozone NAAQS by lowering the standards from 75 ppb to 70 ppb. In November 2017, the EPA designated all counties in the State of Kansas as well as the Missouri counties in KCP&L's and GMO's service territories as attainment/unclassifiable. It is not expected that this will have a material impact on the Evergy Companies' consolidated financial results. If areas surrounding the Evergy Companies' facilities are designated in the future as nonattainment and/or it is required to install additional equipment to control emissions at facilities of the Evergy Companies, it could have a material impact on the operations and consolidated financial results of the Evergy Companies. Greenhouse Gases Burning coal and other fossil fuels releases carbon dioxide (CO 2 ) and other gases referred to as greenhouse gases (GHG). Various regulations under the federal CAA limit CO 2 and other GHG emissions, and in addition, other measures are being imposed or offered by individual states, municipalities and regional agreements with the goal of reducing GHG emissions. In October 2015, the EPA published a rule establishing new source performance standards (NSPS) for GHGs that limit CO 2 emissions for new, modified and reconstructed coal and natural gas fueled electric generating units to various levels per MWh depending on various characteristics of the units. Legal challenges to the GHG NSPS have been filed in the D.C. Circuit by various states and industry members. Also in October 2015, the EPA published a rule establishing guidelines for states to regulate CO 2 emissions from existing power plants. The standards for existing plants are known as the Clean Power Plan (CPP). Under the CPP, interim emissions performance rates must be achieved beginning in 2022 and final emissions performance rates must be achieved by 2030. Legal challenges to the CPP were filed by groups of states and industry members, including Westar Energy, in the D.C. Circuit. The CPP was stayed by the Supreme Court in February 2016 and, accordingly, is not currently being implemented by the states. In April 2017, the EPA published in the Federal Register a notice of withdrawal of the proposed CPP federal plan, proposed model trading rules and proposed Clean Energy Incentive Program design details. Also in April 2017, the EPA published a notice in the Federal Register that it was initiating administrative reviews of the CPP and the GHG NSPS. In October 2017, the EPA issued a proposed rule to repeal the CPP. The proposed rule indicates the CPP exceeds the EPA’s authority and the EPA has not determined whether they will issue a replacement rule. The EPA solicited comments on the legal interpretations contained in this rulemaking. In December 2017, the EPA issued an advance notice of proposed rulemaking to solicit feedback on specific areas of the CPP that could be changed. In August 2018, the EPA published in the Federal Register proposed regulations, which contained (1) emission guidelines for GHG emissions from existing electric utility generating units (EGUs), (2) revisions to emission guideline implementing regulations and (3) revisions to the new source review (NSR) program. The proposed emission guidelines are better known as the Affordable Clean Energy (ACE) Rule. The ACE Rule would establish emission guidelines for states to use in the development of plans to reduce GHG emissions from existing coal-fired EGUs. The ACE Rule is also the replacement rule for the CPP. The ACE rule proposes to determine the "best system of emission reduction" (BSER) for GHG emissions from existing coal-fired EGUs as on-site, heat-rate efficiency improvements. The proposed rule also provides states with a list of candidate technologies that can be used to establish standards of performance and incorporate these performance standards into state plans. In order for the states to be able to effectively implement the proposed emission guidelines contained in the ACE Rule, the EPA is proposing new regulations under 111(d) of the CAA to help clarify this process. In addition, the EPA is proposing revisions to the NSR program that will reduce the likelihood of triggering NSR for proposed heat-rate efficiency improvement projects at existing coal-fired EGUs. The public comment period for these proposed regulatory changes closed on October 31, 2018. In December 2018, the EPA released a proposed rule to revise the existing GHG NSPS for new, modified and reconstructed fossil fuel-fired EGUs, which was issued in October 2015. This proposed rule would determine that BSER for new EGUs is "the most efficient demonstrated steam cycle (e.g. supercritical steam conditions for large units and subcritical steam conditions for small units) in combination with the best operating practices." This replaces the current determination that BSER for these units is the use of partial carbon capture and sequestration technology. The EPA is also proposing to address, in potential future rule making, existing operational limitations imposed by the rule on aero-derivative simple cycle combustion turbines. Due to the future uncertainty of the CPP and ACE rules, the Evergy Companies cannot determine the impact on their operations or consolidated financial results, but the cost to comply with the CPP, should it be upheld and implemented in its current or a substantially similar form, or ACE in its current or a substantially similar form, could be material. Water The Evergy Companies discharge some of the water used in generation and other operations. This water may contain substances deemed to be pollutants. A November 2015 EPA rule establishes effluent limitations guidelines (ELG) and standards for wastewater discharges, including limits on the amount of toxic metals and other pollutants that can be discharged. Implementation timelines for these requirements vary from 2018 to 2023. In April 2017, the EPA announced it is reconsidering the ELG rule and court challenges have been placed in abeyance pending the EPA's review. In September 2017, the EPA finalized a rule to postpone the compliance dates for the new, more stringent, effluent limitations and pretreatment standards for bottom ash transport water and flue gas desulfurization wastewater. These compliance dates have been postponed for two years while the EPA completes its administrative reconsideration of the ELG rule. The Evergy Companies are evaluating the final rule and related developments and cannot predict the resulting impact on their operations or consolidated financial results, but believe costs to comply could be material if the rule is implemented in its current or substantially similar form. In October 2014, the EPA's final standards for cooling intake structures at power plants to protect aquatic life took effect. The standards, based on Section 316(b) of the federal Clean Water Act (CWA), require subject facilities to choose among seven best available technology options to reduce fish impingement. In addition, some facilities must conduct studies to assist permitting authorities to determine whether and what site-specific controls, if any, would be required to reduce entrainment of aquatic organisms. The Evergy Companies' current analysis indicates this rule will not have a significant impact on their coal plants that employ cooling towers or cooling lakes that can be classified as closed cycle cooling and do not expect the impact from this rule to be material. Plants without closed cycle cooling are under evaluation for compliance with these standards and may require additional controls that could be material. KCP&L holds a permit from MDNR covering water discharge from its Hawthorn Station. The permit authorizes KCP&L to, among other things, withdraw water from the Missouri River for cooling purposes and return the heated water to the Missouri River. KCP&L has applied for a renewal of this permit and the EPA has submitted an interim objection letter regarding the allowable amount of heat that can be contained in the returned water. Until this matter is resolved, KCP&L continues to operate under its current permit. Evergy and KCP&L cannot predict the outcome of this matter; however, while less significant outcomes are possible, this matter may require a reduction in generation, installation of cooling towers or other technology to cool the water, or both, any of which could have a material impact on Evergy's and KCP&L's operations and consolidated financial results. In June 2015, the EPA along with the U.S. Army Corps of Engineers issued a final rule, effective August 2015, defining the Waters of the United States (WOTUS) for purposes of the CWA. This rulemaking has the potential to impact all programs under the CWA. Expansion of regulated waterways is possible under the rule depending on regulating authority interpretation, which could impact several permitting programs. Various states and others have filed lawsuits challenging the WOTUS rule. In February 2018, the EPA and the U.S. Army Corps of Engineers finalized a rule adding an applicability date to the 2015 rule, which makes the implementation date of the rule February 2020. In December 2018, the EPA and the U.S. Army Corps of Engineers published in the Federal Register a proposed rule titled "Revised Definition of Waters of the United States. This proposed rule narrows the extent of the CWA jurisdiction as compared to the 2015 rule. The Evergy Companies are currently evaluating the WOTUS rule and related developments, but do not believe the rule, if upheld and implemented in its current or substantially similar form, will have a material impact on the Evergy Companies' operations or consolidated financial results. Regulation of Coal Combustion Residuals In the course of operating their coal generation plants, the Evergy Companies produce CCRs, including fly ash, gypsum and bottom ash. Some of this ash production is recycled, principally by selling to the aggregate industry. The EPA published a rule to regulate CCRs in April 2015, which will require additional CCR handling, processing and storage equipment and closure of certain ash disposal units. The Water Infrastructure Improvements for the Nation (WIIN) Act allows states to achieve delegated authority for CCR rules from the EPA. This has the potential to impact compliance options. In July 2018, KDHE submitted a CCR permit program application to the EPA under authority of the WIIN Act. In November 2018, KDHE received notice from the EPA that its application is deficient and requested additional clarifying information. KDHE has decided it is not going to move forward with additional submittals at this time and will wait until current legal action associated with the CCR rule is final along with planned upcoming modifications to the CCR rule. The Missouri Department of Natural Resources (MDNR) is working on a rule revision, which will allow the state to apply for authority over the federal CCR regulation. The regulation is expected to be promulgated by early 2019. MDNR will then determine when to submit a WIIN Act application to the EPA. Similar to the process in Kansas, this would allow Missouri state regulators to gain control of the CCR program. It will take up to one year from submittal of the Missouri application for the EPA to take final action and grant authority to the state, if such authority is granted. On July 30, 2018, the EPA published in the Federal Register a final rule called the Phase I, Part I CCR Remand Rule in order to modify portions of the 2015 rulemaking. The Phase I, Part I rule provides a timeline extension for unlined impoundments and landfills that must close due to groundwater impacts or location restrictions. The rule also sets risk-based limits for certain groundwater constituents where a maximum contaminant level did not previously exist. These rule modifications add flexibility when assessing compliance. On August 21, 2018, the D.C. Circuit court issued a ruling in the CCR rule litigation between the Utility Solid Waste Activities Group, the EPA and environmental organizations. Portions of the rule were vacated and were remanded back to the EPA for potential modification. Potential revisions to remanded sections could force all unlined surface impoundments to close regardless of groundwater conditions. Any changes to the rule based on this court decision will require additional rulemaking from the EPA. In October 2018, a coalition of environmental groups (including Sierra Club) filed a petition for review in the D.C. Circuit challenging the Phase I, Part I revisions to the CCR Rule. In November 2018, this coalition requested the EPA to stay the October 31, 2020 deadline extension for initiating closure for unlined impoundments and landfills that must close due to groundwater impacts or location restrictions. The EPA has rejected this request and the coalition has filed a petition with the court for a similar stay. If granted, the compliance date will revert to the previously established date in April of 2019. In response, the EPA has filed a motion with the D.C. Circuit to voluntarily remand without vacatur the Part I, Phase I rule. If the October 31, 2020 deadline is modified by either of these actions, then some CCR units in the Evergy Companies' fleet could have to initiate closure on an earlier timeline than what currently exists, but the Evergy Companies do not believe the earlier closure timeline would have a material impact on their operations or consolidated financial results. The Evergy Companies have recorded AROs for their current estimates for the closure of ash disposal ponds, but the revision of these AROs may be required in the future due to changes in existing CCR regulations, the results of groundwater monitoring of CCR units or changes in interpretation of existing CCR regulations or changes in the timing or cost to close ash disposal ponds. If revisions to these AROs are necessary, the impact on the Evergy Companies' operations or consolidated financial results could be material. Storage of Spent Nuclear Fuel Under the Nuclear Waste Policy Act of 1982, the Department of Energy (DOE) is responsible for the permanent disposal of spent nuclear fuel. In 2010, the DOE filed a motion with the Nuclear Regulatory Commission (NRC) to withdraw its then pending application to construct a national repository for the disposal of spent nuclear fuel and high-level radioactive waste at Yucca Mountain, Nevada. The NRC has not yet issued a final decision on the matter. Wolf Creek has elected to build a dry cask storage facility to expand its existing on-site spent nuclear fuel storage, which is expected to provide additional capacity prior to 2022. Wolf Creek has finalized a settlement agreement through 2019 with the DOE for reimbursement of costs to construct this facility that would not have otherwise been incurred had the DOE begun accepting spent nuclear fuel. The Evergy Companies expect the majority of the remaining cost to construct the dry cask storage facility that would not have otherwise been incurred will be reimbursed by the DOE. The Evergy Companies cannot predict when, or if, an off-site storage site or alternative disposal site will be available to receive Wolf Creek's spent nuclear fuel and will continue to monitor this activity. Nuclear Insurance Nuclear liability, property and accidental outage insurance is maintained for Wolf Creek. These policies contain certain industry standard terms, conditions and exclusions, including, but not limited to, ordinary wear and tear and war. An industry aggregate limit of $3.2 billion for nuclear events ( $1.8 billion of non-nuclear events) plus any reinsurance, indemnity or any other source recoverable by Nuclear Electric Insurance Limited (NEIL), provider of property and accidental outage insurance, exists for acts of terrorism affecting Wolf Creek or any other NEIL insured plant within 12 months from the date of the first act. In addition, participation is required in industry-wide retrospect assessment programs as discussed below. Nuclear Liability Insurance Pursuant to the Price-Anderson Act, liability insurance includes coverage against public nuclear liability claims resulting from nuclear incidents to the required limit of public liability, which is approximately $14.1 billion . This limit of liability consists of the maximum available commercial insurance of $0.5 billion and the remaining $13.6 billion is provided through mandatory participation in an industry-wide retrospective assessment program. Under this retrospective assessment program, the owners of Wolf Creek are jointly and severally subject to an assessment of up to $137.6 million (Evergy's share is $129.2 million and each of Westar Energy's and KCP&L's is $64.6 million ), payable at no more than $20.5 million (Evergy's share is $19.2 million and each of Westar Energy's and KCP&L's is $9.6 million ) per incident per year per reactor for any commercial U.S. nuclear reactor qualifying incident. Both the total and yearly assessment is subject to an inflationary adjustment based on the Consumer Price Index and applicable premium taxes. In addition, the U.S. Congress could impose additional revenue-raising measures to pay claims. Nuclear Property and Accidental Outage Insurance The owners of Wolf Creek carry decontamination liability, nuclear property damage and premature nuclear decommissioning liability insurance for Wolf Creek totaling approximately $2.8 billion . Insurance coverage for non-nuclear property damage accidents total approximately $2.3 billion . In the event of an extraordinary nuclear accident, insurance proceeds must first be used for reactor stabilization and site decontamination in accordance with a plan mandated by the NRC. The Evergy Companies' share of any remaining proceeds can be used to pay for property damage or, if certain requirements are met, including decommissioning the plant, toward a shortfall in the nuclear decommissioning trust fund. The owners also carry additional insurance with NEIL to help cover costs of replacement power and other extra expenses incurred during a prolonged outage resulting from accidental property damage at Wolf Creek. If significant losses were incurred at any of the nuclear plants insured under the NEIL policies, the owners of Wolf Creek may be subject to retrospective assessments under the current policies of approximately $37.4 million (Evergy's share is $35.2 million and each of Westar Energy's and KCP&L's is $17.6 million ). Nuclear Insurance Considerations Although the Evergy Companies maintain various insurance policies to provide coverage for potential losses and liabilities resulting from an accident or an extended outage, the insurance coverage may not be adequate to cover the costs that could result from a catastrophic accident or extended outage at Wolf Creek. Any substantial losses not covered by insurance, to the extent not recoverable in prices, would have a material effect on the Evergy Companies' consolidated financial results. Contractual Commitments - Leases The Evergy Companies lease office buildings, computer equipment, vehicles, rail cars and other property and equipment, including rail cars to serve jointly-owned generating units where Westar Energy or KCP&L is the managing partner and are reimbursed by other joint-owners for their proportionate share of the cost. In determining lease expense, the effects of scheduled rent increases on a straight-line basis over the minimum lease term are recognized. Rental expense and estimated future commitments under operating leases are detailed in the following table. Total Operating Leases Evergy Westar Energy KCP&L (a) Rental expense: (millions) 2016 $ 13.6 $ 13.6 $ 13.7 2017 15.7 15.7 13.1 2018 24.5 17.7 11.4 Future commitments: 2019 $ 24.2 $ 14.0 $ 10.2 2020 20.7 10.1 10.6 2021 18.4 8.1 10.3 2022 15.2 5.2 10.0 2023 12.4 2.8 9.6 After 2023 95.0 3.1 91.8 Total $ 185.9 $ 43.3 $ 142.5 (a) KCP&L amounts are only included in consolidated Evergy following the date of the closing of the merger, June 4, 2018. The Evergy Companies identify capital leases based on defined criteria. For both vehicles and computer equipment, new leases are signed each month based on the terms of master lease agreements. Assets recorded under capital leases are detailed in the following table. December 31 2018 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (a) (millions) Vehicles $ 20.2 $ 20.2 $ — $ 19.7 $ 19.7 $ — Computer equipment 0.2 0.2 — 0.9 0.9 — Generation plant 296.7 40.1 — 40.1 40.1 — Other 5.2 — 2.6 — — 2.6 Accumulated amortization (160.0 ) (20.3 ) (1.1 ) (17.1 ) (17.1 ) (1.1 ) Total capital leases $ 162.3 $ 40.2 $ 1.5 $ 43.6 $ 43.6 $ 1.5 (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017. Capital leases are treated as operating leases for rate making purposes. Minimum annual rental payments, excluding administrative costs such as property taxes, insurance and maintenance, under capital leases are detailed in the following table. Total Capital Leases Evergy Westar Energy KCP&L (millions) 2019 $ 6.4 $ 6.0 $ 0.2 2020 5.8 5.4 0.2 2021 5.3 4.9 0.2 2022 4.7 4.3 0.2 2023 4.0 3.6 0.2 After 2023 48.6 46.4 1.1 Total capital lease payments 74.8 70.6 2.1 Amounts representing imputed interest (25.8 ) (24.6 ) (0.6 ) Present value of net minimum lease payments under capital leases 49.0 46.0 1.5 Less: current portion (3.9 ) (3.7 ) (0.1 ) Total long-term obligations under capital leases $ 45.1 $ 42.3 $ 1.4 Contractual Commitments - Fuel, Power and Other The Evergy Companies' contractual commitments at December 31, 2018 , excluding pensions, long-term debt and leases, are detailed in the following tables. Evergy 2019 2020 2021 2022 2023 After 2023 Total Purchase commitments (millions) Fuel $ 423.6 $ 364.4 $ 95.3 $ 82.9 $ 87.5 $ 116.2 $ 1,169.9 Power 47.3 47.3 47.4 47.6 47.8 366.8 604.2 Other 137.8 18.8 13.4 6.8 2.1 34.4 213.3 Total contractual commitments $ 608.7 $ 430.5 $ 156.1 $ 137.3 $ 137.4 $ 517.4 $ 1,987.4 Westar Energy 2019 2020 2021 2022 2023 After 2023 Total Purchase commitments (millions) Fuel $ 240.9 $ 218.1 $ 25.9 $ 45.7 $ 46.9 $ 74.1 $ 651.6 Other 87.4 8.9 5.5 2.2 — — 104.0 Total contractual commitments $ 328.3 $ 227.0 $ 31.4 $ 47.9 $ 46.9 $ 74.1 $ 755.6 KCP&L 2019 2020 2021 2022 2023 After 2023 Total Purchase commitments (millions) Fuel $ 162.6 $ 126.9 $ 69.4 $ 37.2 $ 40.6 $ 42.1 $ 478.8 Power 34.8 34.8 34.9 35.1 35.3 254.5 429.4 Other 34.7 9.0 7.0 3.8 1.6 29.7 85.8 Total contractual commitments $ 232.1 $ 170.7 $ 111.3 $ 76.1 $ 77.5 $ 326.3 $ 994.0 Fuel commitments consist of commitments for nuclear fuel, coal and coal transportation. Power commitments consist of certain commitments for renewable energy under power purchase agreements. Other represents individual commitments entered into in the ordinary course of business.

Guarantees

Guarantees	12 Months Ended
	Dec. 31, 2018
Guarantees [Abstract]
Guarantees	15 . GUARANTEES In the ordinary course of business, Evergy and certain of its subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of certain subsidiaries. Such agreements include, for example, guarantees and letters of credit. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to a subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the subsidiary's intended business purposes. In connection with the closing of the merger, Evergy assumed the guarantees previously provided to GMO by Great Plains Energy. The majority of these agreements guarantee Evergy's own future performance, so a liability for the fair value of the obligation is not recorded. At December 31, 2018 , Evergy has provided $111.3 million of credit support for GMO as follows: • Evergy direct guarantees to GMO counterparties totaling $17.0 million , which expire in 2020 , and • Evergy's guarantee of GMO long-term debt totaling $94.3 million , which includes debt with maturity dates ranging from 2019 to 2023 . Evergy has also guaranteed GMO's commercial paper program . At December 31, 2018 , GMO had $150.0 million of commercial paper outstanding. None of the guaranteed obligations are subject to default or prepayment if GMO's credit ratings were downgraded.

Related Party Transactions and

Related Party Transactions and Relationships	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions and Relationships	16 . RELATED PARTY TRANSACTIONS AND RELATIONSHIPS In the normal course of business, Westar Energy, KCP&L and GMO engage in related party transactions with one another. A summary of these transactions and the amounts associated with them is provided below. All related party transaction amounts between Westar Energy and either KCP&L or GMO only reflect activity between June 4, 2018, the date of the merger, and December 31, 2018 . Jointly-Owned Plants and Shared Services KCP&L employees manage GMO's business and operate its facilities at cost, including GMO's 18% ownership interest in KCP&L's Iatan Nos. 1 and 2. The operating expenses and capital costs billed from KCP&L to GMO were $183.2 million for 2018, $196.3 million for 2017 and $194.4 million for 2016. Westar Energy employees manage Jeffrey Energy Center and operate its facilities at cost, including GMO's 8% ownership interest in Jeffrey Energy Center. The operating expenses and capital costs billed from Westar Energy to GMO for Jeffrey Energy Center and other various business activities were $12.3 million for 2018. KCP&L employees manage La Cygne Station and operate its facilities at cost, including Westar Energy's 50% ownership interest in La Cygne Station. KCP&L and Westar Energy employees also provide one another with shared service support, including costs related to human resources, information technology, accounting and legal services. The operating expenses and capital costs billed from KCP&L to Westar Energy were $82.9 million for 2018. The operating and capital costs billed from Westar Energy to KCP&L were $17.5 million for 2018. Money Pool KCP&L and GMO are also authorized to participate in the Evergy, Inc. money pool, an internal financing arrangement in which funds may be lent on a short-term basis to KCP&L and GMO from Evergy, Inc. and between KCP&L and GMO. At December 31, 2018 and 2017 , KCP&L had no outstanding receivables or payables under the money pool. The following table summarizes Westar Energy's and KCP&L's related party net receivables and payables. December 31 2018 2017 Westar Energy (millions) Net receivable from GMO $ 2.6 $ — Net payable to KCP&L (13.5 ) — Net payable to Evergy (1.4 ) — KCP&L Net receivable from GMO $ 72.6 $ 65.8 Net receivable from Westar Energy 13.5 — Net receivable from Evergy 15.7 — Net receivable from Great Plains Energy — 18.9 Tax Allocation Agreement Evergy files a consolidated federal income tax return as well as unitary and combined income tax returns in several state jurisdictions with Kansas and Missouri being the most significant. Income taxes for consolidated or combined subsidiaries are allocated to the subsidiaries based on separate company computations of income or loss. As of December 31, 2018 , Westar Energy and KCP&L had income taxes receivable from (payable to) Evergy of $42.7 million and $(2.0) million , respectively.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Shareholders' Equity	17 . SHAREHOLDERS' EQUITY Evergy's authorized capital stock consists of 600 million shares of common stock, without par value, and 12 million shares of Preference Stock, without par value. Evergy Registration Statements In November 2018, Evergy filed an automatic shelf registration statement providing for the sale of unlimited amounts of securities with the SEC, which expires in November 2021. In September 2018, Evergy registered shares of its common stock with the SEC for its Dividend Reinvestment and Direct Stock Purchase Plan. Shares issued under the plan may be either newly issued shares or shares purchased on the open market. In June 2018, Evergy registered shares of its common stock with the SEC for the Great Plains Energy 401(k) Savings Plan and Westar Energy, Inc. Employees' 401(k) Savings Plan, among other compensation plans, that Evergy assumed in connection with the merger transaction. Shares issued under the plans may be either newly issued shares or shares purchased on the open market. Common Stock Repurchase Program In July 2018, the Evergy Board authorized the repurchase of up to 60 million shares of Evergy's common stock. Although this repurchase authorization has no expiration date, Evergy expects to repurchase the 60 million shares by mid-2020. Evergy plans to utilize various methods to effectuate the share repurchase program, including but not limited to, a series of transactions that may include accelerated share repurchases, open market transactions or other means, subject to market conditions and applicable legal requirements. The repurchase program may be suspended, discontinued or resumed at any time. For 2018 , Evergy had total repurchases of common stock of approximately $1,042 million and had repurchased 16.4 million shares under the repurchase program. These repurchase totals include shares repurchased under accelerated share repurchase (ASR) agreements, one of which had not reached final settlement as of December 31, 2018, and are discussed further below. Evergy retires repurchased common stock shares in the period the shares are repurchased. In August 2018, Evergy entered into two ASR agreements with financial institutions to purchase $450.0 million of Evergy common stock. The ASR agreements reached final settlement in the fourth quarter of 2018 and resulted in the delivery of 7.9 million shares to Evergy based on the average daily volume weighted-average price of Evergy common stock during the term of the ASR agreements, less a negotiated discount. In November 2018, Evergy entered into an ASR agreement with a financial institution to purchase $475.0 million of Evergy common stock. In December 2018, the financial institution delivered to Evergy 6.4 million shares of common stock, representing a partial settlement of the contract, based on then-current market prices and Evergy paid a total of $475.0 million . The upfront payment was recorded as a reduction to Evergy, Inc. shareholders' equity and as a repurchase of common stock on Evergy's consolidated statements of cash flows. The final number of shares of Evergy common stock that Evergy may receive or be required to remit upon settlement of the ASR agreement will be based on the average daily volume weighted-average price of Evergy common stock during the term of the ASR agreement, less a negotiated discount. Final settlement of the ASR agreement will occur by March 2019, but may occur earlier at the option of the financial institution. Evergy expects that the final settlement of the ASR agreement will result in the delivery of additional shares of common stock to Evergy at no additional cost. Evergy reflects ASRs as a repurchase of common stock in the period the shares are delivered for purposes of calculating earnings per share and as forward contracts indexed to its own common stock. Evergy's ASRs have met all of the applicable criteria for equity classification and therefore are not accounted for as derivative instruments. Dividend Restrictions Evergy depends on its subsidiaries to pay dividends on its common stock. The Evergy Companies have certain restrictions stemming from statutory requirements, corporate organizational documents, covenants and other conditions that could affect dividend levels or the ability to pay dividends. The KCC order authorizing the merger transaction requires Evergy to maintain consolidated common equity of at least 35% of total consolidated capitalization. Under the Federal Power Act, Westar Energy, KCP&L and GMO generally can pay dividends only out of retained earnings. Certain conditions in the MPSC and KCC orders authorizing the merger transaction also require Westar Energy and KCP&L to maintain consolidated common equity of at least 40% of total capitalization. Other conditions in the MPSC and KCC merger orders require Westar Energy, KCP&L and GMO to maintain credit ratings of at least investment grade. If Westar Energy's, KCP&L's or GMO's credit ratings are downgraded below the investment grade level as a result of their affiliation with Evergy or any of Evergy's affiliates, the impacted utility shall not pay a dividend to Evergy without KCC or MPSC approval or until the impacted utility's investment grade credit rating has been restored. The master credit facility of Evergy, Westar Energy, KCP&L and GMO and the note purchase agreement for GMO's Series A, B and C Senior Notes contain covenants requiring the respective company to maintain a consolidated indebtedness to consolidated total capitalization ratio of not more than 0.65 to 1.00 at all times. As of December 31, 2018 , all of Evergy's and Westar Energy's retained earnings and net income were free of restrictions and KCP&L had a retained earnings restriction of $192.0 million . Evergy's subsidiaries had restricted net assets of approximately $5.1 billion as of December 31, 2018 . These restrictions are not expected to affect the Evergy Companies' ability to pay dividends at the current level for the foreseeable future.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	18. VARIABLE INTEREST ENTITIES In determining the primary beneficiary of a VIE, the Evergy Companies assess the entity's purpose and design, including the nature of the entity's activities and the risks that the entity was designed to create and pass through to its variable interest holders. A reporting enterprise is deemed to be the primary beneficiary of a VIE if it has (a) the power to direct the activities of the VIE that most significantly impact the VIE's economic performance and (b) the obligation to absorb losses or right to receive benefits from the VIE that could potentially be significant to the VIE. The primary beneficiary of a VIE is required to consolidate the VIE. The trust holding an 8% interest in Jeffrey Energy Center was a VIE until the expiration of a purchase option in July 2017. The trust holding Westar Energy's 50% interest in La Cygne Unit 2 is a VIE and Westar Energy remains the primary beneficiary of the trust. All involvement with entities by the Evergy Companies is assessed to determine whether such entities are VIEs and, if so, whether or not the Evergy Companies are the primary beneficiaries of the entities. The Evergy Companies also continuously assess whether they are the primary beneficiary of the VIE with which they are involved. Prospective changes in facts and circumstances may cause identification of the primary beneficiary to be reconsidered. 8% Interest in Jeffrey Energy Center Under an agreement with an original expiration of January 2019, Westar Energy leased an 8% interest in Jeffrey Energy Center from a trust. The trust was financed with an equity contribution from an owner participant and debt issued by the trust. The trust was created specifically to purchase the 8% interest in Jeffrey Energy Center and lease it to a third party, and does not hold any other assets. Westar Energy met the requirements to be considered the primary beneficiary of the trust until July 2017, when a contractual option to purchase the 8% interest in the plant covered by the lease expired. Accordingly, Westar Energy deconsolidated the trust in the third quarter of 2017. In February 2019, Westar Energy entered into an agreement to extend the lease of the 8% interest in Jeffrey Energy Center owned by the trust until August 2019. At the expiration of the lease term, Westar Energy will purchase the 8% interest from the trust. 50% Interest in La Cygne Unit 2 Under an agreement that expires in September 2029, Westar Energy entered into a sale-leaseback transaction with a trust under which the trust purchased Westar Energy's 50% interest in La Cygne Unit 2 and subsequently leased it back to Westar Energy. The trust was financed with an equity contribution from an owner participant and debt issued by the trust. The trust was created specifically to purchase the 50% interest in La Cygne Unit 2 and lease it back to Westar Energy, and does not hold any other assets. Westar Energy meets the requirements to be considered the primary beneficiary of the trust. In determining the primary beneficiary of the trust, Westar Energy concluded that the activities of the trust that most significantly impact its economic performance and that Westar Energy has the power to direct include (1) the operation and maintenance of the 50% interest in La Cygne Unit 2 and (2) Westar Energy's ability to exercise a purchase option at the end of the agreement at the lesser of fair value or a fixed amount. Westar Energy has the potential to receive benefits from the trust that could potentially be significant if the fair value of the 50% interest in La Cygne Unit 2 at the end of the agreement is greater than the fixed amount. The following table summarizes the assets and liabilities related to the VIE described above that are recorded on Evergy's and Westar Energy's consolidated balance sheets. December 31 2018 2017 Assets: (millions) Property, plant and equipment of variable interest entities, net $ 169.2 $ 176.3 Liabilities: Current maturities of long-term debt of variable interest entities $ 30.3 $ 28.5 Accrued interest (a) 0.5 0.7 Long-term debt of variable interest entities, net 51.1 81.4 (a) Included in accrued interest on Evergy's and Westar Energy's consolidated balance sheets. All of the liabilities noted in the table above relate to the purchase of the property, plant and equipment of the VIE. The assets of the VIE can be used only to settle obligations of the VIE and the VIE's debt holders have no recourse to the general credit of Evergy and Westar Energy. Evergy and Westar Energy have not provided financial or other support to the VIE and are not required to provide such support. Evergy and Westar Energy did not record any gain or loss upon the initial consolidation of the VIE.

Taxes

Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	19. TAXES Components of income tax expense are detailed in the following tables. Evergy 2018 2017 2016 Current income taxes (millions) Federal $ (67.4 ) $ 0.1 $ (1.0 ) State 2.2 0.4 0.3 Total (65.2 ) 0.5 (0.7 ) Deferred income taxes Federal 160.1 122.8 155.2 State (32.3 ) 30.7 32.9 Total 127.8 153.5 188.1 Investment tax credit Amortization (3.6 ) (2.8 ) (2.9 ) Total (3.6 ) (2.8 ) (2.9 ) Income tax expense $ 59.0 $ 151.2 $ 184.5 Westar Energy 2018 2017 2016 Current income taxes (millions) Federal $ (0.3 ) $ 0.1 $ (1.0 ) State (1.8 ) 0.4 0.3 Total (2.1 ) 0.5 (0.7 ) Deferred income taxes Federal 43.5 122.8 155.2 State (42.9 ) 30.7 32.9 Total 0.6 153.5 188.1 Investment tax credit Amortization (2.8 ) (2.8 ) (2.9 ) Total (2.8 ) (2.8 ) (2.9 ) Income tax expense (benefit) $ (4.3 ) $ 151.2 $ 184.5 KCP&L 2018 2017 2016 Current income taxes (millions) Federal $ 29.8 $ 37.4 $ 24.8 State 8.9 8.3 4.7 Total 38.7 45.7 29.5 Deferred income taxes Federal (3.4 ) 74.7 76.4 State 53.0 8.8 17.0 Total 49.6 83.5 93.4 Investment tax credit Amortization (1.0 ) (1.0 ) (1.0 ) Total (1.0 ) (1.0 ) (1.0 ) Income tax expense $ 87.3 $ 128.2 $ 121.9 Effective Income Tax Rates Effective income tax rates reflected in the financial statements and the reasons for their differences from the statutory federal rates are detailed in the following tables. Evergy 2018 2017 2016 Federal statutory income tax 21.0 % 35.0 % 35.0 % COLI policies (1.9 ) (3.1 ) (4.2 ) State income taxes 4.9 4.1 4.0 Flow through depreciation for plant-related differences 0.8 2.3 3.1 Federal tax credits (6.4 ) (6.9 ) (1.8 ) Non-controlling interest (0.4 ) (0.9 ) (0.9 ) AFUDC equity (0.1 ) (0.2 ) (0.8 ) Amortization of federal investment tax credits (0.6 ) (0.6 ) (0.5 ) Changes in uncertain tax positions, net 0.1 — — Federal or state tax rate change (8.7 ) 2.5 — Valuation allowance 0.4 0.3 0.4 Stock compensation (0.4 ) (0.9 ) (0.5 ) Officer compensation limitation 1.2 0.2 — Other (0.2 ) (0.8 ) — Effective income tax rate 9.7 % 31.0 % 33.8 % Westar Energy 2018 2017 2016 Federal statutory income tax 21.0 % 35.0 % 35.0 % COLI policies (3.3 ) (3.1 ) (4.2 ) State income taxes 5.0 4.1 4.0 Flow through depreciation for plant-related differences 1.6 2.3 3.1 Federal tax credits (10.4 ) (6.9 ) (1.8 ) Non-controlling interest (0.6 ) (0.9 ) (0.9 ) AFUDC equity (0.2 ) (0.2 ) (0.8 ) Amortization of federal investment tax credits (0.8 ) (0.6 ) (0.5 ) Changes in uncertain tax positions, net 0.1 — — Federal or state tax rate change (15.3 ) 2.5 — Valuation allowance 0.5 0.3 0.4 Stock compensation (0.8 ) (0.9 ) (0.5 ) Officer compensation limitation 1.8 0.2 — Other 0.2 (0.8 ) — Effective income tax rate (1.2 )% 31.0 % 33.8 % KCP&L 2018 2017 2016 Federal statutory income tax 21.0 % 35.0 % 35.0 % COLI policies (0.2 ) (0.3 ) (0.2 ) State income taxes 5.5 3.8 4.1 Flow through depreciation for plant-related differences (2.5 ) 0.5 0.3 Federal tax credits (2.1 ) (2.4 ) (3.1 ) AFUDC equity (0.1 ) (0.7 ) (0.7 ) Amortization of federal investment tax credits (0.4 ) (0.3 ) (0.3 ) Federal or state tax rate change 14.1 5.3 — Valuation allowance — 0.4 — Stock compensation — 0.2 — Officer compensation limitation 0.6 0.1 0.2 Other (1.0 ) — (0.1 ) Effective income tax rate 34.9 % 41.6 % 35.2 % Deferred Income Taxes The tax effects of major temporary differences resulting in deferred income tax assets (liabilities) in the consolidated balance sheets is in the following table. December 31 2018 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (a) Deferred tax assets: (millions) Tax credit carryforward $ 508.1 $ 307.1 $ 194.0 $ 276.7 $ 276.7 $ 185.8 Income taxes refundable to customers, net 478.1 233.1 186.9 230.3 230.3 179.1 Deferred employee benefit costs 215.4 89.6 118.3 95.9 95.9 124.6 Net operating loss carryforward 383.3 60.7 119.2 70.0 70.0 131.2 Deferred state income taxes 62.5 62.5 — 63.8 63.8 — Alternative minimum tax carryforward 73.4 26.7 — 52.2 52.2 — Accrued liabilities 82.6 13.6 32.8 13.2 13.2 26.0 Other 193.5 101.7 46.7 97.9 97.9 35.7 Total deferred tax assets before valuation allowance 1,996.9 895.0 697.9 900.0 900.0 682.4 Valuation allowances (27.3 ) (1.7 ) — — — — Total deferred tax assets, net 1,969.6 893.3 697.9 900.0 900.0 682.4 Deferred tax liabilities: Plant-related (3,164.9 ) (1,491.6 ) (1,199.7 ) (1,483.3 ) (1,483.3 ) (1,127.0 ) Deferred employee benefit costs (199.9 ) (89.6 ) (86.1 ) (95.9 ) (95.9 ) (96.0 ) Acquisition premium (72.6 ) (72.6 ) — (76.6 ) (76.6 ) — Other (131.4 ) (54.9 ) (43.9 ) (59.9 ) (59.9 ) (75.5 ) Total deferred tax liabilities (3,568.8 ) (1,708.7 ) (1,329.7 ) (1,715.7 ) (1,715.7 ) (1,298.5 ) Net deferred income tax liabilities $ (1,599.2 ) $ (815.4 ) $ (631.8 ) $ (815.7 ) $ (815.7 ) $ (616.1 ) (a) KCP&L amounts are not included in consolidated Evergy at December 31, 2017. Tax Credit Carryforwards At December 31, 2018 and 2017 , Evergy had $333.8 million and $100.0 million , respectively, of federal general business income tax credit carryforwards. At December 31, 2018 and 2017 , Westar Energy had $134.0 million and $100.0 million , respectively, of federal general business income tax credit carryforwards. At December 31, 2018 and 2017 , KCP&L had $192.8 million and $184.6 million , respectively, of federal general business income tax credit carryforwards. The carryforwards for Evergy, Westar Energy and KCP&L relate primarily to wind production tax credits and advanced coal investment tax credits and expire in the years 2020 to 2038 . Approximately $0.5 million of Evergy's credits are related to Low Income Housing credits that were acquired in Great Plains Energy's acquisition of GMO. Due to federal limitations on the utilization of income tax attributes acquired in the GMO acquisition, Evergy expects a portion of these credits to expire unutilized and has provided a valuation allowance against $0.4 million of the federal income tax benefit. The year of origin of Evergy's, Westar Energy's and KCP&L's related tax benefit amounts for federal tax credit carryforwards as of December 31, 2018 are detailed in the following table. Amount of Benefit Year of Origin Evergy Westar Energy KCP&L (millions) 2000 $ 7.3 $ 7.3 $ — 2001 9.8 9.7 — 2002 0.3 0.2 — 2003 0.3 0.2 — 2004 0.3 0.2 — 2005 0.3 0.2 — 2006 0.3 0.2 — 2007 0.6 0.5 — 2008 39.8 0.5 38.9 2009 47.7 0.2 47.4 2010 18.3 — 18.2 2011 13.3 — 13.2 2012 13.7 2.9 10.7 2013 23.5 10.5 12.9 2014 23.6 10.2 13.0 2015 23.5 10.1 12.8 2016 26.1 10.1 12.4 2017 43.3 34.5 8.2 2018 41.8 36.5 5.1 $ 333.8 $ 134.0 $ 192.8 At December 31, 2018 and 2017 , Evergy had $73.4 million and $52.2 million of federal alternative minimum tax (AMT) credit carryforwards. At December 31, 2018 and 2017, Westar Energy had $26.7 million and $52.2 million of federal AMT carryforwards. These credits do not expire and can be used to reduce taxes paid in the future or become refundable starting in 2018. Due to potential federal budget sequestration reductions for refundable income tax credits, Evergy expects a portion of these credits will not be refunded and has provided a valuation allowance against $7.9 million of the federal income tax benefit. At December 31, 2018 and 2017, Evergy had $174.3 million and $176.7 million , respectively, of tax benefits related to state income tax credit carryforwards. At December 31, 2018 and 2017, Westar Energy had $173.1 million and $176.7 million , respectively, of tax benefit related to state income tax credit carryforwards. At December 31, 2018 and 2017, KCP&L had $1.2 million of tax benefits related to state income tax credit carryforwards. The state income tax credits relate primarily to the Kansas high performance incentive program tax credits and expire in the years 2024 to 2033. Net Operating Loss Carryforwards At December 31, 2018 and 2017 , Evergy had $324.2 million and $38.0 million , respectively, of tax benefits related to federal net operating loss (NOL) carryforwards. At December 31, 2018 and 2017, Westar Energy had $40.1 million and $38.0 million , respectively, of tax benefits related to federal NOL carryforwards. At December 31, 2018 and 2017, KCP&L had $107.5 million and $107.3 million , respectively, of tax benefits related to federal NOL carryforwards. Approximately $78.1 million at December 31, 2018 are tax benefits related to NOLs that were acquired in the GMO acquisition. Due to federal limitations on the utilization of income tax attributes acquired in the GMO acquisition, Evergy expects a portion of these credits to expire unutilized and has provided a valuation allowance against $7.1 million of the federal income tax benefit. The federal NOL carryforwards expire in years 2022 to 2037 . The year of origin of Evergy's, Westar Energy's and KCP&L's related tax benefit amounts for federal NOL carryforwards as of December 31, 2018 are detailed in the following table. Amount of Benefit Year of Origin Evergy Westar Energy KCP&L (millions) 2004 $ 1.6 $ — $ — 2005 44.4 — — 2006 32.0 — — 2009 21.9 — — 2010 2.5 — — 2011 65.3 — 38.4 2012 0.2 0.2 — 2013 1.5 0.8 0.3 2014 77.2 25.0 12.3 2015 59.3 0.2 55.6 2016 0.8 0.4 0.3 2017 16.2 12.3 0.6 2018 1.3 1.2 — $ 324.2 $ 40.1 $ 107.5 In addition, Evergy also had deferred tax benefits of $59.1 million and $26.0 million related to state NOLs as of December 31, 2018 and 2017 , respectively. Westar Energy had deferred tax benefits of $20.6 million and $26.0 million related to state NOLs as of December 31, 2018 and 2017, respectively. KCP&L had deferred tax benefits of $11.7 million and $23.9 million related to state NOLs as of December 31, 2018 and 2017, respectively. The state NOL carryforwards expire in years 2019 to 2037 . Evergy does not expect to utilize $11.9 million of NOLs before the expiration date of the carryforwards of NOLs in certain states. Therefore, a valuation allowance has been provided against $11.9 million of state tax benefits. Valuation Allowances Evergy is required to assess the ultimate realization of deferred tax assets using a "more likely than not" assessment threshold. This assessment takes into consideration tax planning strategies within Evergy's control. As a result of this assessment, Evergy has established a partial valuation allowance for federal and state tax NOL carryforwards and tax credit carryforwards. During 2018 , $0.5 million of tax expense was recorded in continuing operations primarily related to AMT credits offset by the tax benefit recorded for the expiration of certain state NOL carryforwards. The remaining valuation allowances against federal and state NOL carryforwards and tax credit carryforwards were acquired as part of the merger and were recorded as part of the purchase accounting entries. Federal Tax Reform In December 2017, the U.S. Congress passed and President Donald Trump signed Public Law No. 115-97, commonly referred to as the TCJA. The TCJA represents the first major reform in U.S. income tax law since 1986. Most notably, the TCJA reduces the current top corporate income tax rate from 35% to 21% beginning in 2018, repeals the corporate AMT, makes existing AMT tax credit carryforwards refundable, and changes the deductibility and taxability of certain items, among other things. Prior to the change in tax rates that has been reflected in their 2018 rate cases, Westar Energy, KCP&L and GMO recovered the cost of income taxes in rates from their customers based on the 35% federal corporate income tax rate. In January 2018, the KCC issued an order requiring certain regulated public utilities, including Westar Energy and KCP&L, to begin recording a regulatory liability for the difference between the new federal corporate tax rate and amounts currently collected in rates. In the second quarter of 2018, Westar Energy and KCP&L entered into settlement agreements with KCC staff and other intervenors in which they further agreed to begin deferring any impacts of the TCJA on their excess accumulated deferred income taxes to a regulatory liability. The KCC approved these settlement agreements in June 2018. KCP&L and GMO had also recorded regulatory liabilities in 2018 due to the probability that they would also be required to make similar refunds to their Missouri customers. The final regulatory treatment of these regulatory liabilities was determined in each of Westar Energy's, KCP&L's and GMO's rate cases with the KCC and MPSC. See Note 5 for more information and the amounts of the regulatory liabilities recorded by the Evergy Companies. Missouri Tax Reform On June 1, 2018, the Missouri governor signed Senate Bill (S.B.) 884 into law. Most notably, S.B. 884 reduces the corporate income tax rate from 6.25% to 4.0% beginning in 2020, provides for the mandatory use of the single sales factor formula and eliminates intercompany transactions between corporations that file a consolidated Missouri income tax return. As a result of the change in the Missouri corporate income tax rate, KCP&L revalued and restated its deferred income tax assets and liabilities as of June 1, 2018. KCP&L decreased its net deferred income tax liabilities by $46.6 million , primarily consisting of a $28.8 million adjustment for the revaluation and restatement of deferred income tax assets and liabilities included in Missouri jurisdictional rate base and a $9.9 million tax gross-up adjustment for ratemaking purposes. The decrease to KCP&L's net deferred income tax liabilities included in Missouri jurisdictional rate base were offset by a corresponding increase in regulatory liabilities. The net regulatory liabilities will be amortized to customers over a period to be determined in a future rate case. KCP&L recognized $15.5 million of income tax benefit primarily related to the difference between KCP&L's revaluation of its deferred income tax assets and liabilities for financial reporting purposes and the amount of the revaluation pertaining to KCP&L's Missouri jurisdictional rate base.

Quarterly Operating Results (Un

Quarterly Operating Results (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Text Block]	20. QUARTERLY OPERATING RESULTS (UNAUDITED) Quarter Evergy 1st 2nd 3rd 4th 2018 (millions, except per share amounts) Operating revenue $ 600.2 $ 893.4 $ 1,582.5 $ 1,199.8 Operating income 123.5 126.9 533.1 150.1 Net income 62.9 104.4 357.6 21.1 Net income attributable to Evergy, Inc. 60.5 101.8 355.0 18.5 Basic and diluted earnings per common share 0.42 0.56 1.32 0.07 2017 Operating revenue $ 572.6 $ 609.3 $ 794.3 $ 594.8 Operating income 131.4 160.2 264.9 122.3 Net income 63.5 76.0 160.7 36.3 Net income attributable to Evergy, Inc. 59.7 72.1 158.3 33.8 Basic and diluted earnings per common share 0.42 0.50 1.11 0.24 Quarter Westar Energy 1st 2nd 3rd 4th 2018 (millions) Operating revenue $ 600.2 $ 650.9 $ 764.8 $ 599.0 Operating income 123.5 76.1 256.9 94.0 Net income 62.9 77.6 178.0 30.6 Net income attributable to Westar Energy, Inc. 60.5 75.0 175.4 28.0 2017 Operating revenue $ 572.6 $ 609.3 $ 794.3 $ 594.8 Operating income 131.4 160.2 264.9 122.3 Net income 63.5 76.0 160.7 36.3 Net income attributable to Westar Energy, Inc. 59.7 72.1 158.3 33.8 Quarter KCP&L 1st 2nd 3rd 4th 2018 (millions) Operating revenue $ 397.1 $ 452.2 $ 559.6 $ 414.2 Operating income 61.0 114.7 189.4 44.7 Net income (loss) 20.2 24.6 120.3 (2.2 ) 2017 Operating revenue $ 395.9 $ 482.7 $ 595.7 $ 416.4 Operating income 65.0 126.2 219.8 75.4 Net income 14.2 49.6 114.1 1.9 Quarterly data is subject to seasonal fluctuations with peak periods occurring in the summer months. Evergy's results reflect the results of operations of Westar Energy for all periods in 2017. Evergy had separate operations and includes the results of operation of KCP&L and GMO beginning with the quarter ended June 30, 2018. See Note 1 for more information.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Consolidation, Policy [Policy Text Block]	Organization Evergy is a public utility holding company incorporated in 2017 and headquartered in Kansas City, Missouri. Evergy operates primarily through the following wholly-owned direct subsidiaries: • Westar Energy is an integrated, regulated electric utility that provides electricity to customers in the state of Kansas. Westar Energy has one active wholly-owned subsidiary with significant operations, Kansas Gas and Electric Company (KGE). • KCP&L is an integrated, regulated electric utility that provides electricity to customers in the states of Missouri and Kansas. • KCP&L Greater Missouri Operations Company (GMO) is an integrated, regulated electric utility that provides electricity to customers in the state of Missouri. • GPE Transmission Holding Company, LLC (GPETHC) owns 13.5% of Transource Energy, LLC (Transource) with the remaining 86.5% owned by AEP Transmission Holding Company, LLC, a subsidiary of American Electric Power Company, Inc. (AEP). Transource is focused on the development of competitive electric transmission projects. GPETHC accounts for its investment in Transource under the equity method. Westar Energy also owns a 50% interest in Prairie Wind Transmission, LLC (Prairie Wind), which is a joint venture between Westar Energy and affiliates of AEP and Berkshire Hathaway Energy Company. Prairie Wind owns a 108-mile, 345 kV double-circuit transmission line that provides transmission service in the Southwest Power Pool, Inc. (SPP). Westar Energy accounts for its investment in Prairie Wind under the equity method. Westar Energy and KGE conduct business in their respective service territories using the name Westar Energy. KCP&L and GMO conduct business in their respective service territories using the name KCP&L. Collectively, the Evergy Companies have approximately 14,500 MWs of owned generating capacity and renewable purchased power agreements and engage in the generation, transmission, distribution and sale of electricity to approximately 1.6 million customers in the states of Kansas and Missouri. Evergy was incorporated in 2017 as Monarch Energy Holding, Inc. (Monarch Energy), a wholly-owned subsidiary of Great Plains Energy Incorporated (Great Plains Energy). Prior to the closing of the merger transactions, Monarch Energy changed its name to Evergy and did not conduct any business activities other than those required for its formation and matters contemplated by the Amended and Restated Agreement and Plan of Merger, dated as of July 9, 2017, by and among Great Plains Energy, Westar Energy, Monarch Energy and King Energy, Inc. (King Energy), a wholly-owned subsidiary of Monarch Energy (Amended Merger Agreement). On June 4, 2018, in accordance with the Amended Merger Agreement, Great Plains Energy merged into Evergy, with Evergy surviving the merger and King Energy merged into Westar Energy, with Westar Energy surviving the merger. These merger transactions resulted in Evergy becoming the parent entity of Westar Energy and the direct subsidiaries of Great Plains Energy, including KCP&L and GMO. See Note 2 for additional information regarding the merger. Principles of Consolidation Westar Energy was determined to be the accounting acquirer in the merger and thus, the predecessor of Evergy. Therefore, Evergy's consolidated financial statements reflect the results of operations of Westar Energy for 2017 and 2016 and the financial position of Westar Energy as of December 31, 2017. Evergy had separate operations for the period beginning with the quarter ended June 30, 2018, and references to amounts for periods after the closing of the merger relate to Evergy. The results of Great Plains Energy's direct subsidiaries have been included in Evergy's results of operations from the date of the closing of the merger and thereafter. Westar Energy and KCP&L continue to be Securities and Exchange Commission (SEC) registrants. KCP&L has elected not to apply "push-down accounting" related to the merger, whereby the adjustments of assets and liabilities to fair value and the resulting goodwill would be recorded on the financial statements of the acquired subsidiary. These adjustments for KCP&L, as well as those related to the acquired assets and liabilities of Great Plains Energy and its other direct subsidiaries, are only reflected on Evergy's consolidated financial statements. Each of Evergy's, Westar Energy's and KCP&L's consolidated financial statements includes the accounts of their subsidiaries and variable interest entities (VIEs) of which they are the primary beneficiary. Undivided interests in jointly-owned generation facilities are included on a proportionate basis. Intercompany transactions have been eliminated. The Evergy Companies assess financial performance and allocate resources on a consolidated basis (i.e., operate in one segment). Certain changes in classification and corresponding reclassification of prior period data were made in Evergy's, Westar Energy's and KCP&L's consolidated balance sheets, statements of income and comprehensive income and statements of cash flows for comparative purposes. Evergy reflects the classifications of Westar Energy as the accounting acquirer in the merger. These reclassifications did not affect Evergy's, Westar Energy's or KCP&L's net income or Evergy's, Westar Energy's or KCP&L's cash flows from operations, investing or financing. Most significantly for Westar Energy's consolidated balance sheets as of December 31, 2017, was the reclassification of $50.2 million from accrued employee benefits (currently reported as pension and post-retirement liability) to other long-term liabilities. Most significantly for KCP&L's consolidated balance sheets, current regulatory assets and liabilities have been presented separately from the non-current portions in each respective consolidated balance sheet where recovery or refund is expected within the next 12 months.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates The process of preparing financial statements in conformity with generally accepted accounting principles (GAAP) requires the use of estimates and assumptions that affect the reported amounts of certain types of assets, liabilities, revenues and expenses. Such estimates primarily relate to unsettled transactions and events as of the date of the financial statements. Accordingly, upon settlement, actual results may differ from estimated amounts.
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and Cash Equivalents Cash equivalents consist of highly liquid investments with original maturities of three months or less at acquisition.
Fuel Inventory and Supplies	Fuel Inventory and Supplies The Evergy Companies record fuel inventory and supplies at average cost.
Property, Plant and Equipment, Policy [Policy Text Block]	Property, Plant and Equipment The Evergy Companies record the value of property, plant and equipment, including that of variable interest entities (VIEs), at cost. For plant, cost includes contracted services, direct labor and materials, indirect charges for engineering and supervision and an allowance for funds used during construction (AFUDC). AFUDC represents the allowed cost of capital used to finance utility construction activity. AFUDC equity funds are included as a non-cash item in other income and AFUDC borrowed funds are a reduction of interest expense. AFUDC is computed by applying a composite rate to qualified construction work in progress. The rates used to compute gross AFUDC are compounded semi-annually. The amounts of the Evergy Companies' AFUDC for borrowed and equity funds are detailed in the following table. 2018 2017 2016 Evergy (millions) AFUDC borrowed funds $ 10.4 $ 5.6 $ 10.0 AFUDC equity funds 3.1 2.0 11.6 Total $ 13.5 $ 7.6 $ 21.6 Westar Energy AFUDC borrowed funds $ 6.6 $ 5.6 $ 10.0 AFUDC equity funds 2.9 2.0 11.6 Total $ 9.5 $ 7.6 $ 21.6 KCP&L (a) AFUDC borrowed funds $ 4.9 $ 6.1 $ 5.6 AFUDC equity funds 1.4 6.0 6.6 Total $ 6.3 $ 12.1 $ 12.2 (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018 through December 31, 2018. The average rates used in the calculation of AFUDC are detailed in the following table. 2018 2017 2016 Westar Energy 3.3% 2.3% 4.2% KCP&L 3.9% 4.9% 5.7% GMO 2.9% 1.9% 1.6% When property units are retired or otherwise disposed, the original cost net of salvage is charged to accumulated depreciation. Repair of property and replacement of items not considered to be units of property are expensed as incurred, except for planned refueling and maintenance outages at Wolf Creek Generating Station (Wolf Creek). As authorized by regulators, the expense is deferred and amortized ratably over the period between planned outages incremental maintenance cost incurred for such outages.
Depreciation, Depletion, and Amortization [Policy Text Block]	Depreciation and Amortization Depreciation and amortization of utility plant other than nuclear fuel is computed using the straight-line method over the estimated lives of depreciable property based on rates approved by state regulatory authorities. Annual depreciation rates average approximately 3% . Nuclear fuel is amortized to fuel expense based on the quantity of heat produced during the generation of electricity. See Note 7 for more details.
Plant Retirement and Abandonment, Policy [Policy Text Block]	Plant to be Retired, Net When the Evergy Companies retire utility plant, the original cost, net of salvage, is charged to accumulated depreciation. However, when it becomes probable an asset will be retired significantly in advance of its original expected useful life and in the near term, the cost of the asset and related accumulated depreciation is recognized as a separate asset and a probable abandonment. If the asset is still in service, the net amount is classified as plant to be retired, net on the consolidated balance sheets. If the asset is no longer in service, the net amount is classified as a regulatory asset on the consolidated balance sheets. The Evergy Companies must also assess the probability of full recovery of the remaining net book value of the abandonment. The net book value that may be retained as an asset on the balance sheet for the abandonment is dependent upon amounts that may be recovered through regulated rates, including any return. An impairment charge, if any, would equal the difference between the remaining net book value of the asset and the present value of the future revenues expected from the asset. In June 2017, GMO announced the expected retirement of certain older generating units, including GMO's Sibley No. 3 Unit, over the next several years. GMO determined that Sibley No. 3 Unit met the criteria to be considered probable of abandonment. GMO retired Sibley Station, including the No. 3 Unit, in November 2018. As of December 31, 2018 , Evergy has classified the remaining Sibley No. 3 Unit net book value of $159.9 million as retired generation facilities within regulatory assets on its consolidated balance sheet. Evergy is currently allowed a full recovery of and a full return on Sibley No. 3 Unit in rates and has concluded that no impairment is required as of December 31, 2018 .
Asset Retirement Obligation [Policy Text Block]	Nuclear Plant Decommissioning Costs Nuclear plant decommissioning cost estimates are based on either the immediate dismantlement method or the deferred dismantling method as determined by the KCC and MPSC and include the costs of decontamination, dismantlement and site restoration. Based on these cost estimates, Westar Energy and KCP&L contribute to a tax-qualified trust fund to be used to decommission Wolf Creek. Related liabilities for decommissioning are included on Evergy's, Westar Energy's and KCP&L's consolidated balance sheets in Asset Retirement Obligations (AROs). As a result of the authorized regulatory treatment and related regulatory accounting, differences between the decommissioning trust fund asset and the related ARO are recorded as a regulatory asset or liability. See Note 6 for discussion of AROs including those associated with nuclear plant decommissioning costs.
Public Utilities, Policy [Policy Text Block]	Regulatory Accounting Accounting standards are applied that recognize the economic effects of rate regulation. Accordingly, regulatory assets and liabilities have been recorded when required by a regulatory order or based on regulatory precedent. See Note 5 for additional information concerning regulatory matters.
Life Settlement Contracts, Policy [Policy Text Block]	Cash Surrender Value of Life Insurance Amounts related to corporate-owned life insurance (COLI) are recorded on the consolidated balance sheets in other long-terms assets and are detailed in the following table for Evergy. Substantially all of Evergy's COLI-related balances relate to Westar Energy's COLI activity. December 31 2018 2017 Evergy (millions) Cash surrender value of policies $ 1,441.7 $ 1,320.7 Borrowings against policies (1,306.9 ) (1,189.2 ) Corporate-owned life insurance, net $ 134.8 $ 131.5 Increases in cash surrender value and death benefits are recorded in other income in the Evergy Companies' consolidated statements of income and comprehensive income. Interest expense incurred on policy loans is offset against the policy income. Income from death benefits is highly variable from period to period.
Fair Value of Financial Instruments, Policy [Policy Text Block]	Fair Value of Financial Instruments The following methods and assumptions were used to estimate the fair value of the following financial instruments for which it was practicable to estimate that value. Nuclear decommissioning trust fund - The Evergy Companies' nuclear decommissioning trust fund assets are recorded at fair value based on quoted market prices of the investments held by the fund and/or valuation models. Pension plans - For financial reporting purposes, the market value of plan assets is the fair value.
Revenue from Contract with Customer [Policy Text Block]	Revenue Recognition The Evergy Companies recognize revenue on the sale of electricity to customers over time as the service is provided in the amount they have the right to invoice. Revenues recorded include electric services provided but not yet billed by the Evergy Companies. Unbilled revenues are recorded for kWh usage in the period following the customers' billing cycle to the end of the month. This estimate is based on net system kWh usage less actual billed kWhs. The Evergy Companies' estimated unbilled kWhs are allocated and priced by regulatory jurisdiction across the rate classes based on actual billing rates. The Evergy Companies' unbilled revenue estimate is affected by factors including fluctuations in energy demand, weather, line losses and changes in the composition of customer classes. See Note 4 for the balance of unbilled receivables for each of Evergy, Westar Energy and KCP&L as of December 31, 2018 and 2017. The Evergy Companies also collect sales taxes and franchise fees from customers concurrent with revenue-producing activities that are levied by state and local governments. These items are excluded from revenue, and thus are not reflected on the consolidated statements of income and comprehensive income for Evergy, Westar Energy and KCP&L. See Note 3 for additional details regarding revenue recognition from sales of electricity by the Evergy Companies.
Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block]	Allowance for Doubtful Accounts The Evergy Companies determine their allowance for doubtful accounts based on the age of their receivables. Receivables are charged off when they are deemed uncollectible, which is based on a number of factors including specific facts surrounding an account and management's judgment.
Property Gains And Losses [Policy Text Block]	Property Gains and Losses Net gains and losses from the sale of assets and businesses and from asset impairments are recorded in operating expenses.
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]	Asset Impairments Long-lived assets and finite-lived intangible assets subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If the sum of the undiscounted expected future cash flows from an asset to be held and used is less than the carrying value of the asset, an asset impairment must be recognized in the financial statements. The amount of impairment recognized is the excess of the carrying value of the asset over its fair value. Goodwill and indefinite lived intangible assets are tested for impairment annually and when an event occurs indicating the possibility that an impairment exists. The annual test must be performed at the same time each year. Evergy's first impairment test for the $2,338.9 million of goodwill from the Great Plains Energy and Westar Energy merger will be conducted on May 1, 2019. The goodwill impairment test consists of comparing the fair value of a reporting unit to its carrying amount, including goodwill, to identify potential impairment. In the event that the carrying amount exceeds the fair value of the reporting unit, an impairment loss is recognized for the difference between the carrying amount of the reporting unit and its fair value.
Income Tax, Policy [Policy Text Block]	Income Taxes Income taxes are accounted for using the asset/liability approach. Deferred tax assets and liabilities are determined based on the temporary differences between the financial reporting and tax bases of assets and liabilities, applying enacted statutory tax rates in effect for the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion of the deferred tax assets will not be realized. The Evergy Companies recognize tax benefits based on a "more-likely-than-not" recognition threshold. In addition, the Evergy Companies recognize interest accrued related to unrecognized tax benefits in interest expense and penalties in operating expenses. Evergy files a consolidated federal income tax return as well as unitary and combined income tax returns in several state jurisdictions with Kansas and Missouri being the most significant. Income taxes for consolidated or combined subsidiaries are allocated to the subsidiaries based on separate company computations of income or loss. Westar Energy's and KCP&L's income tax provisions include taxes allocated based on their separate company's income or loss. The Evergy Companies have established a net regulatory liability for future refunds to be made to customers for the over-collection of income taxes in rates. Tax credits are recognized in the year generated except for certain Westar Energy, KCP&L and GMO investment tax credits that have been deferred and amortized over the remaining service lives of the related properties.
New Accounting Standards	New Accounting Standards Intangibles - Internal-Use Software In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-15, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , which aligns the requirements for recording implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. An entity in a hosting arrangement that is a service contract will need to determine which project stage (that is, preliminary project stage, application development stage or post-implementation stage) an implementation activity relates. Costs for implementation activities in the application development stage are recorded as a prepaid asset depending on the nature of the costs, while costs incurred during the preliminary project and post-implementation stages are expensed as the activities are incurred. Costs that are recorded to a prepaid asset are to be expensed over the term of the hosting arrangement. The new guidance is effective for annual periods beginning after December 15, 2019, and interim periods within those fiscal years. The new guidance can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. Early adoption is permitted. The Evergy Companies early adopted ASU No. 2018-15 prospectively as of January 1, 2019. The adoption of ASU No. 2018-15 did not have a material impact on the Evergy Companies. Compensation - Retirement Benefits In March 2017, the FASB issued ASU No. 2017-07, Compensation-Retirement Benefits , which requires an employer to disaggregate the service cost component from the other components of net benefit cost. The service cost component is to be reported in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The non-service cost components are to be reported separately from service costs and outside of a subtotal of income from operations. The amendments in this update allow only the service cost component to be eligible for capitalization as part of utility plant. The non-service cost components that are no longer eligible for capitalization as part of utility plant will be recorded as a regulatory asset. The new guidance is to be applied retrospectively for the presentation of service cost and non-service cost components in the income statement and prospectively for the capitalization of the service cost component and is effective for interim and annual periods beginning after December 15, 2017. The Evergy Companies adopted ASU No. 2017-07 on January 1, 2018, and accordingly have retrospectively adjusted prior periods. The Evergy Companies utilized the practical expedient that allows for the use of amounts disclosed in Note 9 for applying the retrospective presentation to the 2017 and 2016 consolidated statements of income and comprehensive income. Statement of Cash Flows In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments , which clarifies how certain cash receipts and cash payments are presented and classified in the statement of cash flows. Among other clarifications, the guidance requires that cash proceeds received from the settlement of COLI policies be classified as cash inflows from investing activities and that cash payments for premiums on COLI policies may be classified as cash outflows for investing activities, operating activities or a combination of both. Retrospective application is required. The Evergy Companies adopted the guidance effective January 1, 2018, which resulted in retrospective reclassification of cash proceeds of $2.8 million and $22.1 million from the settlement of COLI policies from cash inflows from operating activities to cash inflows from investing activities for 2017 and 2016 , respectively, for Evergy and Westar Energy. In addition, cash payments of $3.1 million and $3.4 million for premiums on COLI policies were reclassified from cash outflows used in operating activities to cash outflows used in investing activities for the same periods, respectively, for Evergy and Westar Energy. The adoption of ASU No. 2016-15 did not have a material impact on KCP&L. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows: Restricted Cash , which requires that the statement of cash flows explains the change for the period of restricted cash and restricted cash equivalents along with cash and cash equivalents. The guidance requires a retrospective transition method and is effective for fiscal years beginning after December 15, 2017. The Evergy Companies adopted the guidance effective January 1, 2018. As a result, Evergy and Westar Energy adjusted amounts previously reported for cash and cash equivalents to include restricted cash, which resulted in an increase to beginning and ending cash, cash equivalents and restricted cash of $0.1 million for 2017 and 2016 . The adoption of ASU No. 2016-18 did not have a material impact on KCP&L. Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which requires an entity that is a lessee to record a right-of-use asset and a lease liability for lease payments on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. Lessor accounting remains largely unchanged. In January 2018, the FASB issued ASU No. 2018-01, which permits entities to elect an optional transition practical expedient to not evaluate under Topic 842 land easements that exist or expired before the entity’s adoption of Topic 842 and that were not previously accounted for as leases under Topic 840. In July 2018, the FASB issued ASU No. 2018-10, "Codification Improvements to Topic 842, Leases," which updates narrow aspects of the guidance issued in ASU 2016-02. Also in July 2018, the FASB issued ASU No. 2018-11, "Leases, Targeted Improvements," which provides an optional transition method that allows entities to initially apply the new standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption without restating prior periods. In December 2018, the FASB issued ASU No. 2018-20, "Leases: Narrow-Scope Improvements for Lessors," which is expected to reduce a lessor’s implementation and ongoing costs associated with applying ASU 2016-02. ASU 2016-02 and the subsequent amendments are effective for interim and annual periods beginning after December 15, 2018, with early adoption permitted, and requires a modified retrospective transition approach with an option to either adjust or not adjust comparative periods. The Evergy Companies adopted the new guidance on January 1, 2019, without adjusting comparative periods for all leases existing as of January 1, 2019, by electing the optional transition method permitted by ASU No. 2018-11. As a result, Evergy, Westar Energy and KCP&L recorded an increase to assets and liabilities of approximately $110 million , $40 million and $80 million , respectively, as of January 1, 2019. The Evergy Companies do not expect the impact of adoption of the standard will have a material impact on their consolidated statements of income and comprehensive income. The Evergy Companies will include additional disclosures about its right-of-use assets, lease liabilities and lease expense in the first quarter 2019 notes to financial statements. The Evergy Companies also elected a practical expedient to forgo reassessing existing or expired contracts as leases to determine whether each is in scope of the new standard and to forgo reassessing lease classification for existing and expired leases. Financial Instruments In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities , which generally requires equity investments to be measured at fair value with changes in fair value recognized in net income. Under the new standard, equity securities are no longer to be classified as available-for-sale or trading securities. The guidance requires a modified retrospective transition method. This guidance is effective for fiscal years beginning after December 15, 2017; accordingly, the Evergy Companies adopted the new standard on January 1, 2018, without a material impact on their consolidated financial statements. Revenue Recognition In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. In August 2015, the FASB issued ASU No. 2015-14, deferring the effective date of ASU No. 2014-09 one year, from January 1, 2017, to January 1, 2018. The ASU replaced most existing revenue recognition guidance in GAAP when it became effective. The Evergy Companies adopted ASU No. 2014-09 and its related amendments (Accounting Standards Codification (ASC) 606) on January 1, 2018, using the modified retrospective transition method for all contracts not completed as of the date of adoption. Results for reporting periods beginning after January 1, 2018, are presented under ASC 606 while historical periods have not been adjusted and continue to be reported in accordance with the legacy guidance in ASC 605 - Revenue Recognition . There was no cumulative effect adjustment to the opening balance of retained earnings in 2018 for the Evergy Companies as a result of the adoption of the new guidance. As a result of the adoption of ASC 606, operating revenues and taxes other than income taxes on KCP&L's statements of comprehensive income decreased $76.4 million for 2018 . This impact was related to sales taxes and franchise fees collected from KCP&L's Missouri customers that were included in KCP&L's operating revenues and taxes other than income taxes on KCP&L's statements of comprehensive income prior to the adoption of ASC 606. See Note 3 for more information on revenue from contracts with customers.
Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block]	Principles of Consolidation Westar Energy was determined to be the accounting acquirer in the merger and thus, the predecessor of Evergy. Therefore, Evergy's consolidated financial statements reflect the results of operations of Westar Energy for 2017 and 2016 and the financial position of Westar Energy as of December 31, 2017. Evergy had separate operations for the period beginning with the quarter ended June 30, 2018, and references to amounts for periods after the closing of the merger relate to Evergy. The results of Great Plains Energy's direct subsidiaries have been included in Evergy's results of operations from the date of the closing of the merger and thereafter. Westar Energy and KCP&L continue to be Securities and Exchange Commission (SEC) registrants. KCP&L has elected not to apply "push-down accounting" related to the merger, whereby the adjustments of assets and liabilities to fair value and the resulting goodwill would be recorded on the financial statements of the acquired subsidiary. These adjustments for KCP&L, as well as those related to the acquired assets and liabilities of Great Plains Energy and its other direct subsidiaries, are only reflected on Evergy's consolidated financial statements. Each of Evergy's, Westar Energy's and KCP&L's consolidated financial statements includes the accounts of their subsidiaries and variable interest entities (VIEs) of which they are the primary beneficiary. Undivided interests in jointly-owned generation facilities are included on a proportionate basis. Intercompany transactions have been eliminated. The Evergy Companies assess financial performance and allocate resources on a consolidated basis (i.e., operate in one segment). Certain changes in classification and corresponding reclassification of prior period data were made in Evergy's, Westar Energy's and KCP&L's consolidated balance sheets, statements of income and comprehensive income and statements of cash flows for comparative purposes. Evergy reflects the classifications of Westar Energy as the accounting acquirer in the merger. These reclassifications did not affect Evergy's, Westar Energy's or KCP&L's net income or Evergy's, Westar Energy's or KCP&L's cash flows from operations, investing or financing. Most significantly for Westar Energy's consolidated balance sheets as of December 31, 2017, was the reclassification of $50.2 million from accrued employee benefits (currently reported as pension and post-retirement liability) to other long-term liabilities. Most significantly for KCP&L's consolidated balance sheets, current regulatory assets and liabilities have been presented separately from the non-current portions in each respective consolidated balance sheet where recovery or refund is expected within the next 12 months.
Earnings Per Share, Policy [Policy Text Block]	Earnings Per Share To compute basic earnings per share (EPS), Evergy divides net income attributable to Evergy, Inc. by the weighted average number of common shares outstanding. Diluted EPS includes the effect of issuable common shares resulting from restricted share units (RSUs), performance shares and restricted stock. Evergy computes the dilutive effects of potential issuances of common shares using the treasury stock method. The following table reconciles Evergy's basic and diluted EPS. 2018 2017 2016 Income (millions, except per share amounts) Net income $ 546.0 $ 336.5 $ 361.2 Less: Net income attributable to noncontrolling interests 10.2 12.6 14.6 Net income attributable to Evergy, Inc. $ 535.8 $ 323.9 $ 346.6 Common Shares Outstanding Weighted average number of common shares outstanding - basic 213.9 142.5 142.1 Add: effect of dilutive securities 0.2 0.1 0.4 Diluted average number of common shares outstanding 214.1 142.6 142.5 Basic and Diluted EPS $ 2.50 $ 2.27 $ 2.43 There were no anti-dilutive securities excluded from the computation of diluted EPS for 2018, 2017 and 2016.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Reclassifications	The table below summarizes KCP&L's reclassifications related to operating and investing activities for its consolidated statement of cash flows for 2017 and 2016. 2017 2016 As Previously Filed As Recast As Previously Filed As Recast CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES: (in millions) Adjustments to reconcile income to net cash from operating activities: Amortization of other $ 30.2 $ — $ 33.9 $ — Amortization of deferred refueling outage — 18.3 — 19.0 Deferred income taxes, net 83.5 — 93.4 — Investment tax credit amortization (1.0 ) — (1.0 ) — Net deferred income taxes and credits — 82.5 — 92.4 Payments for asset retirement obligations (25.5 ) (25.5 ) — (15.0 ) Other/Solar rebates paid (a) (9.0 ) 7.5 1.4 8.8 Changes in working capital items: Fuel inventory and supplies — (5.2 ) — 6.3 Fuel inventories (a) 1.9 — 10.6 — Materials and supplies (a) (7.1 ) — (4.3 ) — Prepaid expenses and other current assets — 8.4 — (73.2 ) Other current liabilities — (0.1 ) — 10.4 Changes in other assets — 31.7 — 66.5 Changes in other liabilities — 6.5 — (9.4 ) Deferred refueling outage costs (a) 15.5 — (3.1 ) — Pension and post-retirement benefit obligations (a) 27.3 — 28.6 — Fuel recovery mechanisms (a) 8.3 — (53.7 ) — Total reclassifications $ 124.1 $ 124.1 $ 105.8 $ 105.8 CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES: Additions to property, plant and equipment $ — $ (468.6 ) $ — $ (447.9 ) Utility capital expenditures (437.7 ) — (418.8 ) — Allowance for borrowed funds used during construction (6.1 ) — (5.6 ) — Other investing activities (23.9 ) 0.9 (23.8 ) (0.3 ) Total reclassifications $ (467.7 ) $ (467.7 ) $ (448.2 ) $ (448.2 ) (a) Previously reported within Note 3 to the consolidated financial statements of the Great Plains Energy and KCP&L combined 2017 and 2016 Annual Reports on Form 10-K.
Schedule of Fuel Inventory and Supplies	The following table separately states the balances for fuel inventory and supplies. December 31 2018 2017 Evergy (millions) Fuel inventory $ 168.9 $ 94.1 Supplies 342.1 199.5 Fuel inventory and supplies $ 511.0 $ 293.6 Westar Energy Fuel inventory $ 87.8 $ 94.1 Supplies 189.0 199.5 Fuel inventory and supplies $ 276.8 $ 293.6 KCP&L (a) Fuel inventory $ 57.8 $ 71.0 Supplies 119.8 126.0 Fuel inventory and supplies $ 177.6 $ 197.0 (a) KCP&L amounts are not included in consolidated Evergy at December 31, 2017.
Allowance for funds used during construction [Table Text Block]	The average rates used in the calculation of AFUDC are detailed in the following table. 2018 2017 2016 Westar Energy 3.3% 2.3% 4.2% KCP&L 3.9% 4.9% 5.7% GMO 2.9% 1.9% 1.6%
Depreciable Lives of Property Plant and Equipment [Table Text Block]	The depreciable lives of Evergy's, Westar Energy's and KCP&L's property, plant and equipment are detailed in the following table. Evergy Westar Energy KCP&L (years) Generating facilities 8 to 87 8 to 87 20 to 60 Transmission facilities 15 to 94 36 to 94 15 to 70 Distribution facilities 8 to 73 19 to 73 8 to 55 Other 5 to 84 7 to 84 5 to 50
Cash surrender value of corporate owned life insurance [Table Text Block]	Cash Surrender Value of Life Insurance Amounts related to corporate-owned life insurance (COLI) are recorded on the consolidated balance sheets in other long-terms assets and are detailed in the following table for Evergy. Substantially all of Evergy's COLI-related balances relate to Westar Energy's COLI activity. December 31 2018 2017 Evergy (millions) Cash surrender value of policies $ 1,441.7 $ 1,320.7 Borrowings against policies (1,306.9 ) (1,189.2 ) Corporate-owned life insurance, net $ 134.8 $ 131.5
Other Income (Expense), Net [Table Text Block]	The table below shows the detail of other expense for each of the Evergy Companies. 2018 2017 2016 Evergy (millions) Non-service cost component of net benefit cost $ (47.8 ) $ (20.0 ) $ (20.6 ) Other (30.9 ) (19.1 ) (18.0 ) Other expense $ (78.7 ) $ (39.1 ) $ (38.6 ) Westar Energy Non-service cost component of net benefit cost $ (23.5 ) $ (20.0 ) $ (20.6 ) Other (23.3 ) (19.1 ) (18.0 ) Other expense $ (46.8 ) $ (39.1 ) $ (38.6 ) KCP&L (a) Non-service cost component of net benefit cost $ (25.9 ) $ (42.7 ) $ (37.2 ) Other (5.0 ) (8.1 ) (7.6 ) Other expense $ (30.9 ) $ (50.8 ) $ (44.8 ) (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018 through December 31, 2018.
Schedule of Earnings Per Share, Basic and Diluted	The following table reconciles Evergy's basic and diluted EPS. 2018 2017 2016 Income (millions, except per share amounts) Net income $ 546.0 $ 336.5 $ 361.2 Less: Net income attributable to noncontrolling interests 10.2 12.6 14.6 Net income attributable to Evergy, Inc. $ 535.8 $ 323.9 $ 346.6 Common Shares Outstanding Weighted average number of common shares outstanding - basic 213.9 142.5 142.1 Add: effect of dilutive securities 0.2 0.1 0.4 Diluted average number of common shares outstanding 214.1 142.6 142.5 Basic and Diluted EPS $ 2.50 $ 2.27 $ 2.43
Supplemental Cash Flow Information	Supplemental Cash Flow Information Year Ended December 31 2018 2017 2016 Evergy (millions) Cash paid for (received from): Interest on financing activities, net of amount capitalized $ 255.9 $ 153.9 $ 139.0 Interest on financing activities of VIEs 2.3 3.1 5.8 Income taxes, net of refunds (0.9 ) (12.7 ) 13.1 Non-cash investing transactions: Property, plant and equipment additions (reductions) (7.8 ) 158.8 151.5 Deconsolidation of property, plant and equipment of VIE — (72.9 ) — Non-cash financing transactions: Issuance of stock for compensation and reinvested dividends 0.5 5.1 9.7 Deconsolidation of VIE — (83.1 ) — Assets acquired through capital leases 1.2 4.8 2.7 Year Ended December 31 2018 2017 2016 Westar Energy (millions) Cash paid for (received from): Interest on financing activities, net of amount capitalized $ 155.3 $ 153.9 $ 139.0 Interest on financing activities of VIEs 2.3 3.1 5.8 Income taxes, net of refunds 37.5 (12.7 ) 13.1 Non-cash investing transactions: Property, plant and equipment additions (reductions) (32.5 ) 158.8 151.5 Deconsolidation of property, plant and equipment of VIE — (72.9 ) — Non-cash financing transactions: Issuance of stock for compensation and reinvested dividends — 5.1 9.7 Deconsolidation of VIE — (83.1 ) — Assets acquired through capital leases 1.2 4.8 2.7 Year Ended December 31 2018 2017 2016 KCP&L (a) (millions) Cash paid for (received from): Interest on financing activities, net of amount capitalized $ 129.4 $ 128.0 $ 127.0 Income taxes, net of refunds 31.2 38.8 (37.3 ) Non-cash investing transactions: Property, plant and equipment additions 19.2 36.6 75.4 (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018.
Schedule of Retrospective Adjustments	The following table reflects the retrospective adjustments in the line items of Evergy's, Westar Energy's and KCP&L's consolidated statements of income and comprehensive income associated with the adoption of ASU No. 2017 -07. 2017 2016 As Previously Reported (b) Effect of Change As Reported As Previously Reported (b) Effect of Change As Reported Evergy (millions) Operating and maintenance expense $ 583.5 $ (20.0 ) $ 563.5 $ 607.8 $ (20.6 ) $ 587.2 Total operating expenses 1,912.2 (20.0 ) 1,892.2 1,880.3 (20.6 ) 1,859.7 Income from operations 658.8 20.0 678.8 681.8 20.6 702.4 Other expense (19.1 ) (20.0 ) (39.1 ) (18.0 ) (20.6 ) (38.6 ) Total other income (expense), net (6.8 ) (20.0 ) (26.8 ) 19.1 (20.6 ) (1.5 ) Westar Energy Operating and maintenance expense $ 583.5 $ (20.0 ) $ 563.5 $ 607.8 $ (20.6 ) $ 587.2 Total operating expenses 1,912.2 (20.0 ) 1,892.2 1,880.3 (20.6 ) 1,859.7 Income from operations 658.8 20.0 678.8 681.8 20.6 702.4 Other expense (19.1 ) (20.0 ) (39.1 ) (18.0 ) (20.6 ) (38.6 ) Total other income (expense), net (6.8 ) (20.0 ) (26.8 ) 19.1 (20.6 ) (1.5 ) KCP&L (a) Operating and maintenance expense $ 517.5 $ (42.7 ) $ 474.8 $ 539.2 $ (37.2 ) $ 502.0 Total operating expenses 1,447.0 (42.7 ) 1,404.3 1,393.3 (37.2 ) 1,356.1 Income from operations 443.7 42.7 486.4 482.1 37.2 519.3 Other expense (8.1 ) (42.7 ) (50.8 ) (7.6 ) (37.2 ) (44.8 ) Total other income (expense), net 3.1 (42.7 ) (39.6 ) 4.2 (37.2 ) (33.0 ) (a) KCP&L amounts are not included in consolidated Evergy for 2017 and 2016. (b) Certain Evergy, Westar Energy and KCP&L as previously reported amounts have been adjusted to reflect reclassification adjustments made for comparative purposes as discussed further in Principles of Consolidation above and that have no impact on net income.

Merger of Great Plains Energy_2

Merger of Great Plains Energy and Westar Energy (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Schedule of Accounting Charges and Deferrals Related to Merger	The following pre-tax reductions of revenue, expenses and deferral were recognized following the consummation of the merger and are included in the Evergy Companies' consolidated statements of income and comprehensive income for 2018. Description Income Statement Line Item Expected Payment Period Evergy Westar Energy KCP&L (millions) One-time bill credits Operating revenues 2018 - 2019 $ (59.7 ) $ (23.1 ) $ (22.4 ) Annual bill credits Operating revenues 2019 - 2022 (10.5 ) (7.9 ) (2.6 ) Total impact to operating revenues $ (70.2 ) $ (31.0 ) $ (25.0 ) Charitable contributions and community support Operating and maintenance 2018 - 2027 $ 24.7 $ — $ — Voluntary severance and accelerated equity compensation Operating and maintenance 2018 - 2019 47.9 44.2 2.6 Other transaction and transition costs Operating and maintenance 2018 51.0 21.5 2.1 Reallocation and deferral of merger transition costs Operating and maintenance n/a (47.8 ) (13.8 ) (23.2 ) Total impact to operating and maintenance expense $ 75.8 $ 51.9 $ (18.5 ) Total $ (146.0 ) $ (82.9 ) $ (6.5 )
Schedule of Business Acquisitions by Acquisition, Equity Interest Issued or Issuable [Table Text Block]	The total consideration transferred in the merger is based on the closing stock price of Westar Energy on June 4, 2018 and is calculated as follows. (millions, except share amounts) Great Plains Energy common stock shares outstanding as of June 4, 2018 215,800,074 Great Plains Energy restricted stock awards outstanding as of June 4, 2018 (204,825 ) Great Plains Energy shares to be converted to Evergy shares 215,595,249 Exchange ratio 0.5981 Evergy common stock shares issued to Great Plains Energy shareholders 128,947,518 Closing price of Westar Energy common stock as of June 4, 2018 $ 54.00 Fair value of Evergy shares issued to Great Plains Energy shareholders $ 6,963.2 Fair value of Great Plains Energy's equity compensation awards 12.5 Total purchase price $ 6,975.7
Schedule of Purchase Price Allocation	The preliminary purchase price allocation to Great Plains Energy's assets and liabilities as of June 4, 2018, is detailed in the following table. (millions) Current assets $ 2,151.7 Property, plant and equipment, net 9,179.7 Goodwill 2,338.9 Other long-term assets, excluding goodwill 1,235.9 Total assets $ 14,906.2 Current liabilities 1,673.9 Long-term liabilities, excluding long-term debt 2,898.0 Long-term debt, net 3,358.6 Total liabilities $ 7,930.5 Total purchase price $ 6,975.7
Unaudited Pro Forma Financial Information	The unaudited pro forma financial information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Evergy. 2018 2017 (millions, except per share amounts) Operating revenues $ 5,334.6 $ 5,279.2 Net income attributable to Evergy, Inc. 714.3 468.9 Basic earnings per common share $ 2.67 $ 1.73 Diluted earnings per common share $ 2.67 $ 1.73

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Evergy's, Westar Energy's and KCP&L's revenues disaggregated by customer class are summarized in the following tables. 2018 Evergy Westar Energy KCP&L (a) Revenues (millions) Residential $ 1,578.8 $ 846.4 $ 735.6 Commercial 1,356.4 702.8 794.8 Industrial 527.8 396.4 138.8 Other retail 30.6 20.0 10.4 Total electric retail $ 3,493.6 $ 1,965.6 $ 1,679.6 Wholesale 404.4 346.1 53.5 Transmission 308.1 288.9 14.5 Industrial steam and other 17.9 6.0 4.4 Total revenue from contracts with customers $ 4,224.0 $ 2,606.6 $ 1,752.0 Other 51.9 8.3 71.1 Operating revenues $ 4,275.9 $ 2,614.9 $ 1,823.1 (a) KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018 .

Receivables (Tables)

Receivables (Tables)	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Schedule of Receivables	The Evergy Companies' receivables are detailed in the following table. December 31 2018 2017 Evergy (millions) Customer accounts receivable - billed $ 16.7 $ 165.4 Customer accounts receivable - unbilled 91.2 76.6 Other receivables 95.0 55.4 Allowance for doubtful accounts (9.2 ) (6.7 ) Total $ 193.7 $ 290.7 Westar Energy Customer accounts receivable - billed $ — $ 165.4 Customer accounts receivable - unbilled 16.6 76.6 Other receivables 71.6 55.4 Allowance for doubtful accounts (3.9 ) (6.7 ) Total $ 84.3 $ 290.7 KCP&L (a) Customer accounts receivable - billed $ 7.8 $ 1.6 Customer accounts receivable - unbilled 42.9 67.6 Other receivables 15.8 39.3 Allowance for doubtful accounts (3.8 ) (2.2 ) Total $ 62.7 $ 106.3 (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.
Summary of Bad Debt Expense	The Evergy Companies recorded bad debt expense related to contracts with customers as summarized in the following table. 2018 2017 2016 (millions) Evergy $ 20.2 $ 10.3 $ 11.4 Westar Energy 8.5 10.3 11.4 KCP&L (a) 13.1 7.6 6.3 (a) KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018 .

Rate Matters and Regulation Rat

Rate Matters and Regulation Rate Matters and Regulation (Tables)	12 Months Ended
	Dec. 31, 2018
Rate Matters and Regulation [Abstract]
Schedule of Regulatory Assets [Table Text Block]	December 31 2018 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (a) Regulatory Assets (millions) Pension and post-retirement costs $ 808.2 $ 343.7 $ 361.5 $ 393.9 $ 393.9 $ 379.7 Debt reacquisition costs 113.5 104.1 8.2 109.2 109.2 8.7 Debt fair value adjustment 134.5 — — — — — Asset retirement obligations fair value 111.4 — — — — — Depreciation 58.0 58.0 — 60.6 60.6 — Cost of removal 102.4 65.7 36.7 30.8 30.8 30.3 Asset retirement obligations 171.9 49.5 91.6 42.7 42.7 94.3 Analog meter unrecovered investment 35.6 35.6 — 31.5 31.5 — Treasury yield hedges 23.7 23.7 — 24.8 24.8 — Iatan No. 1 and common facilities 7.4 — 2.9 — — 12.9 Iatan No. 2 construction accounting costs 26.8 — 13.5 — — 25.0 Kansas property tax surcharge 33.1 23.7 9.4 17.4 17.4 6.6 Disallowed plant costs 15.0 15.0 — 15.2 15.2 — La Cygne environmental costs 14.8 12.2 2.6 13.3 13.3 2.7 Deferred customer programs 19.9 7.0 8.0 8.1 8.1 40.9 Fuel recovery mechanisms 91.2 7.1 41.7 20.7 20.7 61.7 Solar rebates 45.2 — 13.9 — — 22.6 Transmission delivery charge 0.8 — 0.8 — — 3.2 Wolf Creek outage 21.8 10.9 10.9 7.0 7.0 6.8 Pension and other post-retirement benefit 13.6 5.2 4.8 — — — Retired generation facilities 159.9 — — — — — Merger transition costs 47.0 22.6 17.3 — — — Other regulatory assets 6.1 13.5 2.3 9.7 9.7 3.3 Total 2,061.8 797.5 626.1 784.9 784.9 698.7 Less: current portion (303.9 ) (97.1 ) (130.9 ) (99.5 ) (99.5 ) (153.6 ) Total noncurrent regulatory assets $ 1,757.9 $ 700.4 $ 495.2 $ 685.4 $ 685.4 $ 545.1 (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.
Schedule of Regulatory Liabilities [Table Text Block]	December 31 2018 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (a) Regulatory Liabilities (millions) Taxes refundable through future rates $ 1,703.6 $ 853.2 $ 609.2 $ 845.2 $ 845.2 $ 574.0 Deferred regulatory gain from sale 59.1 59.1 — 64.6 64.6 — Emission allowances 54.1 — 54.1 — — 58.1 Nuclear decommissioning 188.2 84.5 103.7 55.5 55.5 126.0 Pension and post-retirement costs 53.4 28.3 25.1 48.4 48.4 12.0 Jurisdictional allowance for funds used 30.3 30.3 — 31.7 31.7 — La Cygne leasehold dismantling costs 29.5 29.5 — 29.6 29.6 — Cost of removal 48.1 — — — — — Kansas tax credits 16.5 16.5 — 16.8 16.8 — Purchase power agreement 8.8 8.8 — 8.8 8.8 — Merger customer credits 7.5 — 7.5 — — — Refund of tax reform benefits 70.9 7.2 36.3 — — — Other regulatory liabilities 59.0 3.9 11.2 5.0 5.0 9.1 Total 2,329.0 1,121.3 847.1 1,105.6 1,105.6 779.2 Less: current portion (110.2 ) (19.5 ) (52.8 ) (11.6 ) (11.6 ) (8.3 ) Total noncurrent regulatory liabilities $ 2,218.8 $ 1,101.8 $ 794.3 $ 1,094.0 $ 1,094.0 $ 770.9 (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract]
Schedule of Change in Asset Retirement Obligation	The following table summarizes the change in the Evergy Companies' AROs. Evergy Westar Energy KCP&L (a) 2018 2017 2018 2017 2018 2017 (millions) Beginning balance $ 405.1 $ 324.0 $ 405.1 $ 324.0 $ 266.3 $ 278.0 Liabilities assumed upon merger with Great Plains Energy 412.2 — — — — — Liabilities incurred during the year 7.4 13.5 7.4 13.5 — — Revision in timing and/or estimates (150.1 ) 66.8 (138.7 ) 66.8 (11.4 ) 0.3 Settlements (22.4 ) (16.0 ) (12.0 ) (16.0 ) (13.1 ) (25.5 ) Accretion 34.9 16.8 19.3 16.8 19.2 13.5 Ending balance $ 687.1 $ 405.1 $ 281.1 $ 405.1 $ 261.0 $ 266.3 Less: current portion (49.8 ) (25.1 ) (17.1 ) (25.1 ) (29.2 ) (34.9 ) Total noncurrent asset retirement obligation $ 637.3 $ 380.0 $ 264.0 $ 380.0 $ 231.8 $ 231.4 (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018 .

Property, Plant & Equipment P_2

Property, Plant & Equipment Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Public Utility Property, Plant, and Equipment [Table Text Block]	December 31, 2018 Evergy Westar Energy KCP&L (millions) Electric plant in service $ 26,916.7 $ 13,176.7 $ 10,439.1 Electric plant acquisition adjustment 740.6 740.6 — Accumulated depreciation (9,694.1 ) (4,642.8 ) (4,022.4 ) Plant in service 17,963.2 9,274.5 6,416.7 Construction work in progress 685.2 376.7 204.4 Nuclear fuel, net 133.1 66.1 67.0 Plant to be retired, net (b) 1.0 1.0 — Net property, plant and equipment $ 18,782.5 $ 9,718.3 $ 6,688.1 December 31, 2017 Evergy Westar Energy KCP&L (a) (millions) Electric plant in service $ 12,954.3 $ 12,954.3 $ 10,213.2 Electric plant acquisition adjustment 739.0 739.0 — Accumulated depreciation (4,651.7 ) (4,651.7 ) (4,070.3 ) Plant in service 9,041.6 9,041.6 6,142.9 Construction work in progress 434.9 434.9 350.3 Nuclear fuel, net 71.4 71.4 72.4 Plant to be retired, net (b) 5.9 5.9 — Net property, plant and equipment $ 9,553.8 $ 9,553.8 $ 6,565.6
Property_Plant_&_Equipment_of_VIEs [Table Text Block]	December 31 2018 2017 (millions) Electric plant of VIEs $ 392.1 $ 392.1 Accumulated depreciation of VIEs (222.9 ) (215.8 ) Net property, plant and equipment of VIEs $ 169.2 $ 176.3
Depreciation_Expense [Table Text Block]	2018 2017 2016 (millions) Evergy (a) $ 567.9 $ 350.0 $ 316.7 Westar Energy (a) 371.3 350.0 316.7 KCP&L 235.3 228.4 215.4

Jointly Owned Electric Utilit_2

Jointly Owned Electric Utility Plants (Tables)	12 Months Ended
	Dec. 31, 2018
Jointly Owned Electric Utility Plants [Abstract]
Schedule of Jointly Owned Utility Plants [Table Text Block]	Evergy's, Westar Energy's and KCP&L's share of jointly-owned electric utility plants at December 31, 2018 , are detailed in the following tables. Evergy Wolf Creek Unit La Cygne Units (a) Iatan No. 1 Unit Iatan No. 2 Unit Iatan Common Jeffrey Energy Center (b) State Line (millions, except MW amounts) Evergy's share 94% 100% 88% 73% 79% 100% 40% Utility plant in service $ 3,724.9 $ 2,228.0 $ 707.3 $ 1,374.5 $ 504.9 $ 2,392.5 $ 114.1 Accumulated depreciation 1,760.8 737.1 257.3 426.7 127.8 861.0 71.3 Nuclear fuel, net 133.1 — — — — — — Construction work in progress 171.6 41.8 27.1 30.5 26.5 33.2 0.4 2019 accredited capacity-MWs 1,104 1,398 616 641 NA 2,187 196 (a) The VIE consolidated by Evergy and Westar Energy holds its 50% leasehold interest in La Cygne Unit 2. This 50% leasehold interest in La Cygne Unit 2 is reflected in the information provided above. See Note 7 for additional information. (b) Evergy and Westar Energy's 8% leasehold interest in Jeffrey Energy Center is reflected in the information provided above. Westar Energy Wolf Creek Unit La Cygne Units (a) Jeffrey Energy Center (b) State Line (millions, except MW amounts) Westar Energy's share 47% 50% 92% 40% Utility plant in service $ 1,833.7 $ 1,033.5 $ 2,189.6 $ 114.1 Accumulated depreciation 825.3 408.6 778.6 71.3 Nuclear fuel, net 66.1 — — — Construction work in progress 83.7 34.0 30.6 0.4 2019 accredited capacity-MWs 552 699 2,012 196 (a) The VIE consolidated by Evergy and Westar Energy holds its 50% leasehold interest in La Cygne Unit 2. This 50% leasehold interest in La Cygne Unit 2 is reflected in the information provided above. See Note 7 for additional information. (b) Evergy's and Westar Energy's 8% leasehold interest in Jeffrey Energy Center is reflected in the information provided above. KCP&L Wolf Creek Unit La Cygne Units Iatan No. 1 Unit Iatan No. 2 Unit Iatan Common (millions, except MW amounts) KCP&L's share 47% 50% 70% 55% 61% Utility plant in service $ 1,891.2 $ 1,194.5 $ 567.4 $ 1,060.3 $ 414.8 Accumulated depreciation 935.5 328.5 203.2 378.4 112.8 Nuclear fuel, net 67.0 — — — — Construction work in progress 87.9 7.8 3.3 6.2 15.0 2019 accredited capacity-MWs 552 699 490 482 NA

Pension Plans and Other Emplo_2

Pension Plans and Other Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Schedule of Net Benefit Costs	Pension Benefits Post-Retirement Benefits Year Ended December 31, 2016 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Components of net periodic benefit costs (millions) Service cost $ 25.3 $ 25.3 $ 42.0 $ 1.2 $ 1.2 $ 2.6 Interest cost 53.4 53.4 52.9 5.9 5.9 6.1 Expected return on plan assets (52.3 ) (52.3 ) (49.2 ) (6.9 ) (6.9 ) (3.0 ) Prior service cost 0.8 0.8 0.7 0.5 0.5 1.2 Recognized net actuarial (gain) loss 24.9 24.9 51.8 (1.1 ) (1.1 ) (1.5 ) Net periodic benefit costs before regulatory adjustment and intercompany allocations 52.1 52.1 98.2 (0.4 ) (0.4 ) 5.4 Regulatory adjustment 16.4 16.4 (3.1 ) (1.9 ) (1.9 ) 3.6 Intercompany allocations n/a — (36.0 ) n/a — (1.9 ) Net periodic benefit costs 68.5 68.5 59.1 (2.3 ) (2.3 ) 7.1 Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities Current year net (gain) loss 62.8 62.8 63.6 3.1 3.1 1.0 Amortization of gain (loss) (24.9 ) (24.9 ) (51.8 ) 1.1 1.1 1.5 Prior service cost (3.4 ) (3.4 ) — — — (10.1 ) Amortization of prior service cost (0.8 ) (0.8 ) (0.7 ) (0.5 ) (0.5 ) (1.2 ) Other regulatory activity — — (2.9 ) — — (1.9 ) Total recognized in OCI or regulatory asset/liability 33.7 33.7 8.2 3.7 3.7 (10.7 ) Total recognized in net periodic benefit costs and OCI or regulatory asset/liability $ 102.2 $ 102.2 $ 67.3 $ 1.4 $ 1.4 $ (3.6 ) Pension Benefits Post-Retirement Benefits Year Ended December 31, 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Components of net periodic benefit costs (millions) Service cost $ 28.7 $ 28.7 $ 44.2 $ 1.2 $ 1.2 $ 2.1 Interest cost 52.4 52.4 52.6 5.5 5.5 5.4 Expected return on plan assets (53.6 ) (53.6 ) (51.2 ) (6.9 ) (6.9 ) (2.5 ) Prior service cost 0.7 0.7 0.7 0.5 0.5 — Recognized net actuarial (gain) loss 26.9 26.9 49.0 (0.8 ) (0.8 ) (0.5 ) Settlement and special termination benefits 0.4 0.4 16.3 — — — Net periodic benefit costs before regulatory adjustment and intercompany allocations 55.5 55.5 111.6 (0.5 ) (0.5 ) 4.5 Regulatory adjustment 14.5 14.5 (9.2 ) (1.9 ) (1.9 ) 1.3 Intercompany allocations n/a — (37.1 ) n/a — (1.5 ) Net periodic benefit costs 70.0 70.0 65.3 (2.4 ) (2.4 ) 4.3 Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities Current year net (gain) loss 47.1 47.1 71.3 (5.8 ) (5.8 ) 3.0 Amortization of gain (loss) (26.9 ) (26.9 ) (64.9 ) 0.8 0.8 0.5 Amortization of prior service cost (0.7 ) (0.7 ) (0.7 ) (0.5 ) (0.5 ) — Other regulatory activity — — 6.1 — — — Total recognized in OCI or regulatory asset/liability 19.5 19.5 11.8 (5.5 ) (5.5 ) 3.5 Total recognized in net periodic benefit costs and OCI or regulatory asset/liability $ 89.5 $ 89.5 $ 77.1 $ (7.9 ) $ (7.9 ) $ 7.8 Pension Benefits Post-Retirement Benefits Year Ended December 31, 2018 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Components of net periodic benefit costs (millions) Service cost $ 60.7 $ 32.2 $ 48.6 $ 2.3 $ 1.3 $ 2.0 Interest cost 82.5 50.7 49.9 8.0 5.0 4.8 Expected return on plan assets (86.4 ) (55.9 ) (55.5 ) (8.8 ) (7.0 ) (2.8 ) Prior service cost 0.7 0.7 0.7 0.5 0.5 0.1 Recognized net actuarial (gain) loss 32.6 32.6 45.1 (0.6 ) (0.6 ) (0.2 ) Net periodic benefit costs before regulatory adjustment and intercompany allocations 90.1 60.3 88.8 1.4 (0.8 ) 3.9 Regulatory adjustment 8.3 8.8 0.7 (1.7 ) (2.0 ) (0.1 ) Intercompany allocations n/a — (21.6 ) n/a — (1.1 ) Net periodic benefit costs 98.4 69.1 67.9 (0.3 ) (2.8 ) 2.7 Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities Current year net (gain) loss 67.2 (13.2 ) 25.9 4.9 11.7 (14.0 ) Amortization of gain (loss) (32.6 ) (32.6 ) (45.1 ) 0.6 0.6 0.2 Prior service cost 13.4 11.4 2.0 — — — Amortization of prior service cost (0.7 ) (0.7 ) (0.7 ) (0.5 ) (0.5 ) (0.1 ) Other regulatory activity — — 0.6 — — — Total recognized in OCI or regulatory asset/liability 47.3 (35.1 ) (17.3 ) 5.0 11.8 (13.9 ) Total recognized in net periodic benefit costs and OCI or regulatory asset/liability $ 145.7 $ 34.0 $ 50.6 $ 4.7 $ 9.0 $ (11.2 )
Schedule of Net Funded Status [Table Text Block]	Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Change in projected benefit obligation (PBO) (millions) PBO at January 1, 2018 $ 1,367.0 $ 1,367.0 $ 1,331.7 $ 138.6 $ 138.6 $ 133.2 Service cost 60.7 32.2 48.6 2.3 1.3 2.0 Interest cost 82.5 50.7 49.9 8.0 5.0 4.8 Contribution by participants — — — 5.6 1.8 6.6 Plan amendments 13.4 11.4 2.0 — — — Actuarial (gain) loss (98.8 ) (100.1 ) (89.6 ) (11.3 ) (2.6 ) (18.0 ) Benefits paid (137.9 ) (97.9 ) (70.2 ) (17.3 ) (10.5 ) (12.9 ) Obligations assumed upon merger with Great Plains Energy 1,275.9 — — 123.4 — — Other (9.4 ) (4.4 ) — — — — PBO at December 31, 2018 $ 2,553.4 $ 1,258.9 $ 1,272.4 $ 249.3 $ 133.6 $ 115.7 Change in plan assets Fair value of plan assets at January 1, 2018 $ 887.0 $ 887.0 $ 848.4 $ 124.1 $ 124.1 $ 115.8 Actual return on plan assets (79.7 ) (30.9 ) (60.1 ) (7.5 ) (7.4 ) (1.2 ) Contributions by employer and participants 114.5 47.9 80.3 11.6 3.2 11.4 Benefits paid (134.0 ) (95.0 ) (69.8 ) (16.7 ) (10.2 ) (12.4 ) Assets acquired upon merger with Great Plains Energy 825.0 — — 111.8 — — Other (9.4 ) (4.4 ) — — — — Fair value of plan assets at December 31, 2018 $ 1,603.4 $ 804.6 $ 798.8 $ 223.3 $ 109.7 $ 113.6 Funded status at December 31, 2018 $ (950.0 ) $ (454.3 ) $ (473.6 ) $ (26.0 ) $ (23.9 ) $ (2.1 ) Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Change in projected benefit obligation (PBO) (millions) PBO at January 1, 2017 $ 1,241.0 $ 1,241.0 $ 1,220.6 $ 136.8 $ 136.8 $ 130.1 Service cost 28.7 28.7 44.2 1.2 1.2 2.1 Interest cost 52.4 52.4 52.6 5.5 5.5 5.4 Contribution by participants — — — 1.5 1.5 6.0 Actuarial loss 107.0 107.0 134.9 2.8 2.8 2.1 Benefits paid (62.1 ) (62.1 ) (34.7 ) (9.2 ) (9.2 ) (12.5 ) Settlements and special termination benefits — — (85.9 ) — — — PBO at December 31, 2017 $ 1,367.0 $ 1,367.0 $ 1,331.7 $ 138.6 $ 138.6 $ 133.2 Change in plan assets Fair value of plan assets at January 1, 2017 $ 797.2 $ 797.2 $ 776.8 $ 115.6 $ 115.6 $ 115.6 Actual return on plan assets 113.1 113.1 114.8 15.6 15.6 1.8 Contributions by employer and participants 36.3 36.3 76.9 1.9 1.9 10.4 Benefits paid (59.6 ) (59.6 ) (34.5 ) (9.0 ) (9.0 ) (12.0 ) Settlements — — (85.6 ) — — — Fair value of plan assets at December 31, 2017 $ 887.0 $ 887.0 $ 848.4 $ 124.1 $ 124.1 $ 115.8 Funded status at December 31, 2017 $ (480.0 ) $ (480.0 ) $ (483.3 ) $ (14.5 ) $ (14.5 ) $ (17.4 )
Schedule of Amounts Recognized in Balance Sheet [Table Text Block]	Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Amounts recognized in the consolidated balance sheets (millions) Non-current asset $ — $ — $ — $ — $ — $ 12.8 Current pension and other post-retirement liability (2.5 ) (2.5 ) (0.6 ) (0.8 ) (0.8 ) (0.8 ) Noncurrent pension liability and other post-retirement liability (477.5 ) (477.5 ) (482.7 ) (13.7 ) (13.7 ) (29.4 ) Net amount recognized before regulatory treatment (480.0 ) (480.0 ) (483.3 ) (14.5 ) (14.5 ) (17.4 ) Accumulated OCI or regulatory asset/liability 372.6 372.6 379.7 (11.1 ) (11.1 ) (12.2 ) Net amount recognized at December 31, 2017 $ (107.4 ) $ (107.4 ) $ (103.6 ) $ (25.6 ) $ (25.6 ) $ (29.6 ) Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost: Actuarial (gain) loss $ 369.0 $ 369.0 $ 245.5 $ (13.3 ) $ (13.3 ) $ 2.8 Prior service cost 3.6 3.6 2.5 2.2 2.2 (8.0 ) Other — — 131.7 — — (7.0 ) Net amount recognized at December 31, 2017 $ 372.6 $ 372.6 $ 379.7 $ (11.1 ) $ (11.1 ) $ (12.2 ) Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Amounts recognized in the consolidated balance sheets (millions) Non-current asset $ — $ — $ — $ 17.5 $ — $ 17.5 Current pension and other post-retirement liability (4.4 ) (2.6 ) (0.5 ) (1.7 ) (0.9 ) (0.8 ) Noncurrent pension liability and other post-retirement liability (945.6 ) (451.7 ) (473.1 ) (41.8 ) (23.0 ) (18.8 ) Net amount recognized before regulatory treatment (950.0 ) (454.3 ) (473.6 ) (26.0 ) (23.9 ) (2.1 ) Accumulated OCI or regulatory asset/liability 419.9 337.5 362.4 (6.0 ) 0.8 (26.0 ) Net amount recognized at December 31, 2018 $ (530.1 ) $ (116.8 ) $ (111.2 ) $ (32.0 ) $ (23.1 ) $ (28.1 ) Amounts in accumulated OCI or regulatory asset/liability not yet recognized as a component of net periodic benefit cost: Actuarial (gain) loss $ 403.6 $ 323.2 $ 226.3 $ (7.8 ) $ (1.0 ) $ (11.0 ) Prior service cost 16.3 14.3 3.8 1.8 1.8 (8.1 ) Other — — 132.3 — — (6.9 ) Net amount recognized at December 31, 2018 $ 419.9 $ 337.5 $ 362.4 $ (6.0 ) $ 0.8 $ (26.0 )
Schedule of Amounts in Accumulated Other Comprehensive Income (Loss) to be Recognized over Next Fiscal Year [Table Text Block]	Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (millions) Actuarial (gain) loss amortization $ 27.5 $ 25.4 $ 48.3 $ (1.2 ) $ (0.5 ) $ (1.5 ) Prior service cost amortization 1.9 1.7 0.9 0.5 0.5 —
Schedule of Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]	December 31, 2018 Evergy Westar Energy KCP&L (millions) ABO for all defined benefit pension plans $ 2,257.9 $ 1,139.1 $ 1,096.7 Pension plans with the PBO in excess of plan assets Projected benefit obligation $ 2,553.4 $ 1,258.9 $ 1,272.4 Fair value of plan assets 1,603.4 804.6 798.8 Pension plans with the ABO in excess of plan assets Accumulated benefit obligation $ 2,257.9 $ 1,139.1 $ 1,096.7 Fair value of plan assets 1,603.4 804.6 798.8 Other post-retirement benefit plans with the APBO in excess of plan assets Accumulated other post-retirement benefit obligation $ 249.3 $ 133.6 $ 57.7 Fair value of plan assets 223.3 109.7 38.2 December 31, 2017 Evergy Westar Energy KCP&L (millions) ABO for all defined benefit pension plans $ 1,219.6 $ 1,219.6 $ 1,155.5 Pension plans with the PBO in excess of plan assets Projected benefit obligation $ 1,367.0 $ 1,367.0 $ 1,331.7 Fair value of plan assets 887.0 887.0 848.4 Pension plans with the ABO in excess of plan assets Accumulated benefit obligation $ 1,219.6 $ 1,219.6 $ 1,155.5 Fair value of plan assets 887.0 887.0 848.4 Other post-retirement benefit plans with the APBO in excess of plan assets Accumulated other post-retirement benefit obligation $ 138.6 $ 138.6 $ 111.6 Fair value of plan assets 124.1 124.1 81.5
Schedule of Assumptions Used [Table Text Block]	Weighted-average assumptions used to determine the benefit obligation at December 31, 2018 Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Discount rate 4.35 % 4.35 % 4.36 % 4.33 % 4.33 % 4.33 % Rate of compensation increase 3.76 % 4.03 % 3.64 % 3.50 % n/a 3.50 % Weighted-average assumption used to determine the benefit obligation at December 31, 2017 Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Discount rate 3.73 % 3.73 % 3.72 % 3.67 % 3.67 % 3.64 % Rate of compensation increase 4.00 % 4.00 % 3.62 % 4.00 % 4.00 % 3.50 % Weighted-average assumptions used to determine net costs for the year ended December 31, 2018 Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Discount rate 3.73 % 3.73 % 3.72 % 3.67 % 3.73 % 3.64 % Expected long-term return on plan assets 6.52 % 6.67 % 6.46 % 6.00 % 6.00 % 2.80 % Rate of compensation increase 3.92 % 4.00 % 3.62 % 3.50 % n/a 3.50 % Weighted-average assumptions used to determine net costs for the year ended December 31, 2017 Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L Discount rate 4.25 % 4.25 % 4.31 % 4.31 % 4.31 % 4.20 % Expected long-term return on plan assets 6.64 % 6.64 % 6.73 % 6.00 % 6.00 % 2.00 % Rate of compensation increase 4.00 % 4.00 % 3.62 % 4.00 % 4.00 % 3.50 %
Schedule of Expected Benefit Payments [Table Text Block]	Pension Benefits Post-Retirement Benefits Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (millions) 2019 $ 193.0 $ 96.7 $ 94.9 $ 20.3 $ 10.9 $ 9.4 2020 188.9 94.9 92.8 19.8 11.0 8.9 2021 189.4 95.3 92.8 20.6 11.3 9.3 2022 187.4 92.7 93.4 21.1 11.5 9.6 2023 186.1 90.0 94.7 21.5 11.7 9.8 2024-2028 928.7 432.7 488.3 110.7 58.5 52.1
Schedule of Plan Assets Target Allocations [Table Text Block]	Pension Benefits Post-Retirement Benefits Westar Energy KCP&L Westar Energy KCP&L Domestic equities 29 % 32 % 52 % 3 % International equities 20 % 21 % 13 % — % Bonds 36 % 36 % 35 % 85 % Mortgage & asset backed securities — % — % — % 4 % Real estate investments 4 % 6 % — % — % Other investments 11 % 5 % — % 8 %
Schedule of Allocation of Plan Assets [Table Text Block]	Fair Value Measurements Using Description December 31 Level 1 Level 2 Level 3 Assets measured at NAV (millions) Westar Energy Post-Retirement Benefit Plans Domestic equities $ 56.4 $ — $ — $ — $ 56.4 International equities 14.0 — — — 14.0 Bond funds 38.4 — — — 38.4 Short-term investments 0.7 — — — 0.7 Cash and cash equivalents 0.2 0.2 — — — Total $ 109.7 $ 0.2 $ — $ — $ 109.5 KCP&L Post-Retirement Benefit Plans Domestic equities $ 2.5 $ 2.5 $ — $ — $ — International equities 0.9 0.9 — — — Bond funds 75.0 0.2 — — 74.8 Corporate bonds 17.4 — 17.4 — — U.S. Treasury and agency bonds 10.3 2.6 7.7 — — Mortgage and asset backed securities 2.5 — 2.5 — — Cash and cash equivalents 4.7 4.7 — — — Other 0.3 — 0.3 — — Total $ 113.6 $ 10.9 $ 27.9 $ — $ 74.8 Fair Value Measurements Using Description December 31 Level 1 Level 2 Level 3 Assets measured at NAV (millions) Westar Energy Post-Retirement Benefit Plans (a) Domestic equities $ 65.2 $ — $ 65.2 $ — $ — International equities 16.2 — 16.2 — — Bond funds 42.1 — 42.1 — — Cash and cash equivalents 0.6 — 0.6 — — Total $ 124.1 $ — $ 124.1 $ — $ — KCP&L Post-Retirement Benefit Plans Domestic equities $ 3.7 $ 3.7 $ — $ — $ — Bond funds 56.6 0.2 — — 56.4 Corporate bonds 16.7 — 16.7 — — U.S. Treasury and agency bonds 8.5 3.0 5.5 — — Mortgage and asset backed securities 3.6 — 3.6 — — Cash and cash equivalents 25.3 25.3 — — — Other 1.4 — 1.4 — — Total $ 115.8 $ 32.2 $ 27.2 $ — $ 56.4 (a) In 2018, Evergy and Westar Energy re-evaluated the classification, within the fair value hierarchy, of their various fund investments within the Westar Energy Post-Retirement Benefit Plans. As a result, Evergy and Westar Energy determined that certain fund investments within the Westar Energy Post-Retirement Benefit Plans in the amount of $124.1 million as of December 31, 2017, should have been measured using the NAV per share (or its equivalent) practical expedient, instead of as a Level 2 investment. This determination is based on the fact that these funds do not meet the definition of readily determinable fair value due to the absence of a published NAV. Evergy and Westar Energy have determined that this error is immaterial to their current and previously filed financial reports and accordingly, have not revised prior periods but have reflected the changes in fair value hierarchy classification as of December 31, 2018. Fair Value Measurements Using Description December 31 Level 1 Level 2 Level 3 Assets measured at NAV (millions) Westar Energy Pension Plans Domestic equities $ 215.0 $ 144.7 $ — $ — $ 70.3 International equities 138.7 91.8 — — 46.9 Bond funds 296.4 255.4 — — 41.0 Real estate investments 44.8 — — — 44.8 Combination debt/equity/other fund 30.1 30.1 — — — Alternative investment funds 73.6 — — — 73.6 Short-term investments 6.0 — — — 6.0 Total $ 804.6 $ 522.0 $ — $ — $ 282.6 KCP&L Pension Plans Domestic equities $ 238.1 $ 198.6 $ — $ — $ 39.5 International equities 150.9 104.0 — — 46.9 Bond funds 67.4 19.3 — — 48.1 Corporate bonds 123.6 — 123.6 — — U.S. Treasury and agency bonds 69.9 52.4 17.5 — — Mortgage and asset backed securities 5.5 — 5.5 — — Real estate investments 48.2 12.6 — — 35.6 Combination debt/equity/other fund 13.5 13.5 — — — Alternative investment funds 31.6 — — — 31.6 Cash and cash equivalents 49.8 49.8 — — — Other 0.3 — 0.3 — — Total $ 798.8 $ 450.2 $ 146.9 $ — $ 201.7 Fair Value Measurements Using Description December 31 Level 1 Level 2 Level 3 Assets measured at NAV (millions) Westar Energy Pension Plans (a) Domestic equities $ 256.1 $ — $ 232.2 $ — $ 23.9 International equities 177.9 — 177.9 — — Bond funds 299.5 — 299.5 — — Real estate investments 41.8 — — — 41.8 Combination debt/equity/other fund 36.2 — 36.2 — — Alternative investment funds 70.3 — 17.0 — 53.3 Short-term investments 5.2 — 5.2 — — Total $ 887.0 $ — $ 768.0 $ — $ 119.0 KCP&L Pension Plans Domestic equities $ 263.9 $ 220.5 $ — $ — $ 43.4 International equities 176.0 123.5 — — 52.5 Bond funds 71.8 21.4 — — 50.4 Corporate bonds 125.8 — 125.8 — — U.S. Treasury and agency bonds 69.8 51.5 18.3 — — Mortgage and asset backed securities 5.9 — 5.9 — — Real estate investments 46.4 13.6 — — 32.8 Combination debt/equity/other fund 15.9 15.9 — — — Alternative investment funds 32.7 — — — 32.7 Cash and cash equivalents 35.6 35.6 — — — Other 4.6 — 4.6 — — Total $ 848.4 $ 482.0 $ 154.6 $ — $ 211.8 (a) In 2018, Evergy and Westar Energy re-evaluated the classification, within the fair value hierarchy, of their various fund investments within the Westar Energy Pension Plans. As a result, Evergy and Westar Energy determined that certain fund investments within the Westar Energy Pension Plans in the amount of $607.6 million as of December 31, 2017, should have been classified as Level 1, instead of Level 2. This determination is based on the fact that the fair value of these funds is based on daily published prices at which Evergy and Westar Energy are able to redeem their investments without restriction on a daily basis. Evergy and Westar Energy also determined that certain fund investments within the Westar Energy Pension Plans in the amount of $160.4 million as of December 31, 2017, should have been measured using the NAV per share (or its equivalent) practical expedient, instead of as a Level 2 investment. This determination is based on the fact that these funds do not meet the definition of readily determinable fair value due to the absence of a published NAV. Evergy and Westar Energy have determined that these errors are immaterial to their current and previously filed financial reports and accordingly, have not revised prior periods but have reflected the changes in fair value hierarchy classification as of December 31, 2018.
Schedule of Health Care Cost Trend Rates [Table Text Block]	Assumed annual health care cost growth rates as of December 31, 2018 Evergy Westar Energy KCP&L Health care cost trend rate assumed for next year 6.5 % 6.5 % 6.5 % Rate to which the cost trend is assumed to decline (the ultimate trend rate) 4.5 % 4.5 % 4.5 % Year that rate reaches ultimate trend 2027 2027 2027 Assumed annual health care cost growth rates as of December 31, 2017 Evergy Westar Energy KCP&L Health care cost trend rate assumed for next year 6.0 % 6.0 % 6.8 % Rate to which the cost trend is assumed to decline (the ultimate trend rate) 5.0 % 5.0 % 4.5 % Year that rate reaches ultimate trend 2020 2020 2027
Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]	Evergy Westar Energy (a) KCP&L Effect of 1% increase (millions) Effect on total service and interest component $ — $ — $ 0.1 Effect on post-retirement benefit obligation 0.2 (0.1 ) — Effect of 1% decrease Effect on total service and interest component $ — $ — $ 0.3 Effect on post-retirement benefit obligation (0.1 ) 0.1 (0.2 ) (a) Westar Energy includes only the effect of health care cost trend rates for Wolf Creek because the Westar Energy post-retirement benefit plan includes a fixed monthly stipend for health care and therefore is not affected by changes in health care costs.
Schedule of Costs of Retirement Plans [Table Text Block]	2018 2017 2016 (millions) Evergy $ 16.3 $ 9.7 $ 9.6 Westar Energy 9.9 9.7 9.6 KCP&L 8.3 7.7 8.0

Equity Compensation (Tables)

Equity Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity compensation expense and associated income tax benefits	The following table summarizes the Evergy Companies' equity compensation expense and the associated income tax benefit. 2018 2017 2016 Evergy (millions) Equity compensation expense $ 30.7 $ 8.9 $ 9.2 Income tax benefit 1.4 3.5 3.7 Westar Energy Equity compensation expense $ 24.8 $ 8.9 $ 9.2 Income tax benefit 1.4 3.5 3.7 KCP&L (a) Equity compensation expense $ 6.5 $ 4.2 $ 3.2 Income tax benefit 0.1 1.6 1.0 (a) KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through December 31, 2018 .
Performance share activity	Performance share activity for 2018 is summarized in the following table. Performance Shares Grant Date Fair Value* Beginning balance January 1, 2018 — $ — Converted Great Plains Energy awards upon merger 351,708 63.79 Forfeited (3,212 ) 63.44 Ending balance December 31, 2018 348,496 63.80 * weighted-average
Restricted stock activity	Restricted stock activity for 2018 is summarized in the following table. Nonvested Restricted Stock Grant Date Fair Value* Beginning balance January 1, 2018 — $ — Converted Great Plains Energy awards upon merger 122,505 54.05 Vested (4,760 ) 54.50 Forfeited (1,070 ) 54.04 Ending balance December 31, 2018 116,675 54.03 * weighted-average
Restricted stock unit activity	RSU activity for awards with only service requirements for 2018 is summarized in the following table. Nonvested Restricted Share Units Grant Date Fair Value* Beginning balance January 1, 2018 255,964 $ 46.09 Granted 222,465 52.16 Converted Great Plains Energy awards upon merger 82,331 53.77 Vested (342,599 ) 46.81 Forfeited (905 ) 50.73 Ending balance December 31, 2018 217,256 54.07 * weighted-average

Short-term Borrowings and Sho_2

Short-term Borrowings and Short-term Bank Lines of Credit (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Short-term Debt [Table Text Block]	The following table summarizes the committed credit facilities (excluding receivable sale facilities discussed in Note 4) available to the Evergy Companies as of December 31, 2018 and 2017 . Amounts Drawn Credit Facility Commercial Paper Letters of Credit Cash Borrowings Available Borrowings Weighted Average Interest Rate on Short-Term Borrowings December 31, 2018 (millions) Evergy, Inc. $ 450.0 n/a $ 1.0 $ — $ 449.0 —% Westar Energy 1,000.0 411.7 18.3 — 570.0 3.08% KCP&L 600.0 176.9 2.7 — 420.4 2.95% GMO 450.0 150.0 2.1 — 297.9 3.00% Evergy $ 2,500.0 $ 738.6 $ 24.1 $ — $ 1,737.3 December 31, 2017 Westar Energy (b) $ 979.3 $ 275.7 $ 11.8 $ — $ 691.8 1.83% KCP&L (a) 600.0 167.5 2.7 — 429.8 1.95% Evergy 979.3 275.7 11.8 — 691.8 1.83% (a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017 . (b) $20.7 million of Westar Energy's $730.0 million and $270.0 million revolving credit facilities expired in September 2017.

Long-Term Debt Long-Term Debt (

Long-Term Debt Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Debt [Table Text Block]	The Evergy Companies' long-term debt is detailed in the following tables. December 31, 2018 Issuing Entity Year Due Evergy Westar Energy KCP&L Mortgage Bonds (millions) 5.10% Series Westar Energy, Inc. 2020 $ 250.0 $ 250.0 $ — 3.25% Series Westar Energy, Inc. 2025 250.0 250.0 — 2.55% Series Westar Energy, Inc. 2026 350.0 350.0 — 3.10% Series Westar Energy, Inc. 2027 300.0 300.0 — 4.125% Series Westar Energy, Inc. 2042 550.0 550.0 — 4.10% Series Westar Energy, Inc. 2043 430.0 430.0 — 4.625% Series Westar Energy, Inc. 2043 250.0 250.0 — 4.25% Series Westar Energy, Inc. 2045 300.0 300.0 — 6.70% Series KGE 2019 300.0 300.0 — 6.15% Series KGE 2023 50.0 50.0 — 6.53% Series KGE 2037 175.0 175.0 — 6.64% Series KGE 2038 100.0 100.0 — 4.30% Series KGE 2044 250.0 250.0 — 2.95% EIRR bonds KCP&L 2023 79.5 — 79.5 7.15% Series 2009A (8.59% rate) (a) KCP&L 2019 400.0 — 400.0 9.44% Series GMO 2019-2021 3.4 — — Pollution Control Bonds 2.46% Series (b) Westar Energy, Inc. 2032 45.0 45.0 — 2.46% Series (b) Westar Energy, Inc. 2032 30.5 30.5 — 2.46% Series (b) KGE 2027 21.9 21.9 — 2.50% Series KGE 2031 50.0 50.0 — 2.46% Series (b) KGE 2032 14.5 14.5 — 2.46% Series (b) KGE 2032 10.0 10.0 — 1.865% Series 2007A and 2007B (b) KCP&L 2035 146.5 — 146.5 2.75% Series 2008 KCP&L 2038 23.4 — 23.4 Senior Notes 3.15% Series KCP&L 2023 300.0 — 300.0 3.65% Series KCP&L 2025 350.0 — 350.0 6.05% Series (5.78% rate) (a) KCP&L 2035 250.0 — 250.0 5.30% Series KCP&L 2041 400.0 — 400.0 4.20% Series KCP&L 2047 300.0 — 300.0 4.20% Series KCP&L 2048 300.0 — 300.0 8.27% Series GMO 2021 80.9 — — 3.49% Series A GMO 2025 36.0 — — 4.06% Series B GMO 2033 60.0 — — 4.74% Series C GMO 2043 150.0 — — 4.85% Series Evergy, Inc. (g) 2021 350.0 — — 5.292% Series Evergy, Inc. (g) 2022 287.5 — — Medium Term Notes 7.33% Series GMO 2023 3.0 — — 7.17% Series GMO 2023 7.0 — — Fair value adjustment (f) 144.8 — — Current maturities (c) (705.4 ) (300.0 ) (400.0 ) Unamortized debt discount and debt issuance costs (57.2 ) (37.1 ) (19.3 ) Total excluding current maturities (d) $ 6,636.3 $ 3,389.8 $ 2,130.1 December 31, 2017 Issuing Entity Year Due Evergy Westar Energy KCP&L (e) Mortgage Bonds (millions) 5.10% Series Westar Energy, Inc. 2020 $ 250.0 $ 250.0 $ — 3.25% Series Westar Energy, Inc. 2025 250.0 250.0 — 2.55% Series Westar Energy, Inc. 2026 350.0 350.0 — 3.10% Series Westar Energy, Inc. 2027 300.0 300.0 — 4.125% Series Westar Energy, Inc. 2042 550.0 550.0 — 4.10% Series Westar Energy, Inc. 2043 430.0 430.0 — 4.625% Series Westar Energy, Inc. 2043 250.0 250.0 — 4.25% Series Westar Energy, Inc. 2045 300.0 300.0 — 6.70% Series KGE 2019 300.0 300.0 — 6.15% Series KGE 2023 50.0 50.0 — 6.53% Series KGE 2037 175.0 175.0 — 6.64% Series KGE 2038 100.0 100.0 — 4.30% Series KGE 2044 250.0 250.0 — 2.95% EIRR bonds KCP&L 2023 — — 79.5 7.15% Series 2009A (8.59% rate) (a) KCP&L 2019 — — 400.0 Pollution Control Bonds 1.92% Series (b) Westar Energy, Inc. 2032 45.0 45.0 — 1.94% Series (b) Westar Energy, Inc. 2032 30.5 30.5 — 2.00% Series (b) KGE 2027 21.9 21.9 — 2.50% Series KGE 2031 50.0 50.0 — 2.00% Series (b) KGE 2032 14.5 14.5 — 2.00% Series (b) KGE 2032 10.0 10.0 — 1.329% Series 2007A and 2007B (b) KCP&L 2035 — — 146.5 2.875% Series 2008 KCP&L 2038 — — 23.4 Senior Notes 6.375% Series (7.49% rate) (a) KCP&L 2018 — — 350.0 3.15% Series KCP&L 2023 — — 300.0 3.65% Series KCP&L 2025 — — 350.0 6.05% Series (5.78% rate) (a) KCP&L 2035 — — 250.0 5.30% Series KCP&L 2041 — — 400.0 4.20% Series KCP&L 2047 — — 300.0 Current maturities — — (350.0 ) Unamortized debt discount and debt issuance costs (39.3 ) (39.3 ) (17.2 ) Total excluding current maturities (d) $ 3,687.6 $ 3,687.6 $ 2,232.2 (a) Rate after amortizing gains/losses recognized in other comprehensive income (OCI) on settlements of interest rate hedging instruments. (b) Variable rate. (c) Evergy's current maturities total as of December 31, 2018 , includes $4.3 million of fair value adjustments recorded in connection with purchase accounting for the merger transaction. (d) At December 31, 2018 and 2017 , does not include $50.0 million and $21.9 million of secured Series 2005 Environmental Improvement Revenue Refunding (EIRR) bonds because the bonds were repurchased in September 2015 and are held by KCP&L. (e) KCP&L amounts are not included in consolidated Evergy at December 31, 2017. (f) Represents the fair value adjustments recorded at Evergy consolidated related to the long-term debt of Great Plains Energy, KCP&L and GMO in connection with purchase accounting for the merger transaction. This amount is not part of future principal payments and will amortize over the remaining life of the associated debt instruments. (g) Originally issued by Great Plains Energy but assumed by Evergy, Inc. as part of the merger transaction. The following table summarizes Evergy's and Westar Energy's long-term debt of VIEs. December 31 2018 2017 (millions) 2.398% due 2021 $ 81.4 $ 109.9 Current maturities (30.3 ) (28.5 ) Total excluding current maturities $ 51.1 $ 81.4
Schedule of Maturities of Long-term Debt [Table Text Block]	in the following table. 2019 2020 2021 2022 2023 (millions) Evergy (a) $ 701.1 $ 251.1 $ 432.0 $ 287.5 $ 439.5 Westar Energy (a) 300.0 250.0 — — 50.0 KCP&L 400.0 — — — 379.5 VIEs 30.3 32.3 18.8 — — (a) Excludes long-term debt maturities of VIEs.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Carrying value and fair value of debt instruments	The Evergy Companies measure the fair value of long-term debt using Level 2 measurements available as of the measurement date. The book value and fair value of the Evergy Companies' long-term debt and long-term debt of variable interest entities is summarized in the following table. December 31 2018 2017 Book Value Fair Value Book Value Fair Value Long-term debt (a) (millions) Evergy (b) $ 7,341.7 $ 7,412.1 $ 3,687.6 $ 4,010.6 Westar Energy 3,689.8 3,771.3 3,687.6 4,010.6 KCP&L (c) 2,530.1 2,637.5 2,582.2 2,799.1 Long-term debt of variable interest entities (a) Evergy $ 81.4 $ 81.3 $ 109.9 $ 110.8 Westar Energy 81.4 81.3 109.9 110.8 (a) Includes current maturities. (b) Book value as of December 31, 2018 , includes $144.8 million of fair value adjustments recorded in connection with purchase accounting for the Great Plains Energy and Westar Energy merger, which are not part of future principal payments and will amortize over the remaining life of the associated debt instrument. See Note 2 for more information regarding the merger transaction. (c) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.
Fair value of assets and liabilities	The following tables include the Evergy Companies' balances of financial assets and liabilities measured at fair value on a recurring basis. Description December 31, 2018 Level 1 Level 2 Level 3 NAV Westar Energy (millions) Assets Nuclear decommissioning trust (a) Domestic equity funds $ 70.6 $ 63.9 $ — $ — $ 6.7 International equity funds 36.2 36.2 — — — Core bond fund 37.5 37.5 — — — High-yield bond fund 18.9 18.9 — — — Emerging markets bond fund 15.4 15.4 — — — Combination debt/equity/other fund 12.9 12.9 — — — Alternative investments fund 24.1 — — — 24.1 Real estate securities fund 11.8 — — — 11.8 Cash equivalents 0.1 0.1 — — — Total nuclear decommissioning trust 227.5 184.9 — — 42.6 Rabbi trust Core bond fund 24.8 — — — 24.8 Combination debt/equity/other fund 5.6 — — — 5.6 Cash equivalents 0.2 0.2 — — — Total rabbi trust 30.6 0.2 — — 30.4 Total $ 258.1 $ 185.1 $ — $ — $ 73.0 KCP&L Assets Nuclear decommissioning trust (a) Equity securities $ 166.6 $ 166.6 $ — $ — $ — Debt securities U.S. Treasury 42.1 42.1 — — — U.S. Agency 0.4 — 0.4 — — State and local obligations 2.1 — 2.1 — — Corporate bonds 30.9 — 30.9 — — Foreign governments 0.1 — 0.1 — — Cash equivalents 1.7 1.7 — — — Other 0.7 0.7 — — — Total nuclear decommissioning trust 244.6 211.1 33.5 — — Self-insured health plan trust (b) Equity securities 0.5 0.5 — — — Debt securities 3.9 0.3 3.6 — — Cash and cash equivalents 8.0 8.0 — — — Total self-insured health plan trust 12.4 8.8 3.6 — — Total $ 257.0 $ 219.9 $ 37.1 $ — $ — Other Evergy Assets Rabbi trusts Fixed income fund $ 13.2 $ — $ — $ — $ 13.2 Total rabbi trusts $ 13.2 $ — $ — $ — $ 13.2 Liabilities Interest rate swaps (e) $ 5.4 $ — $ 5.4 $ — $ — Total $ 5.4 $ — $ 5.4 $ — $ — Evergy Assets Nuclear decommissioning trust (a) $ 472.1 $ 396.0 $ 33.5 $ — $ 42.6 Rabbi trusts 43.8 0.2 — — 43.6 Self-insured health plan trust (b) 12.4 8.8 3.6 — — Total $ 528.3 $ 405.0 $ 37.1 $ — $ 86.2 Liabilities Interest rate swaps (e) $ 5.4 $ — $ 5.4 $ — $ — Total $ 5.4 $ — $ 5.4 $ — $ — Description December 31, 2017 Level 1 Level 2 Level 3 NAV Westar Energy (millions) Assets Nuclear decommissioning trust (a)(c) Domestic equity funds $ 73.8 $ — $ 68.7 $ — $ 5.1 International equity funds 47.9 — 47.9 — — Core bond fund 33.3 — 33.3 — — High-yield bond fund 18.1 — 18.1 — — Emerging markets bond fund 17.3 — 17.3 — — Combination debt/equity/other fund 14.1 — 14.1 — — Alternative investments fund 21.7 — — — 21.7 Real estate securities fund 10.8 — — — 10.8 Cash equivalents 0.1 0.1 — — — Total nuclear decommissioning trust 237.1 0.1 199.4 — 37.6 Rabbi trust (c) Core bond fund 27.3 — 27.3 — — Combination debt/equity/other fund 6.8 — 6.8 — — Cash equivalents 0.2 0.2 — — — Total rabbi trust 34.3 0.2 34.1 — — Total $ 271.4 $ 0.3 $ 233.5 $ — $ 37.6 KCP&L (d) Assets Nuclear decommissioning trust (a) Equity securities $ 183.8 $ 183.8 $ — $ — $ — Debt securities U.S. Treasury 35.3 35.3 — — — U.S. Agency 0.4 — 0.4 — — State and local obligations 2.1 — 2.1 — — Corporate bonds 34.1 — 34.1 — — Foreign governments 0.1 — 0.1 — — Cash equivalents 2.5 2.5 — — — Other 0.1 0.1 — — — Total nuclear decommissioning trust 258.4 221.7 36.7 — — Self-insured health plan trust (b) Equity securities 0.5 0.5 — — — Debt securities 2.7 0.3 2.4 — — Cash and cash equivalents 7.7 7.7 — — — Total self-insured health plan trust 10.9 8.5 2.4 — — Total $ 269.3 $ 230.2 $ 39.1 $ — $ — Evergy Assets Nuclear decommissioning trust (a)(c) $ 237.1 $ 0.1 $ 199.4 $ — $ 37.6 Rabbi trust (c) 34.3 0.2 34.1 — — Total $ 271.4 $ 0.3 $ 233.5 $ — $ 37.6 (a) Fair value is based on quoted market prices of the investments held by the trust and/or valuation models. (b) Fair value is based on quoted market prices of the investments held by the trust. Debt securities classified as Level 1 are comprised of U.S. Treasury securities. Debt securities classified as Level 2 are comprised of corporate bonds, U.S. Agency, state and local obligations, and other asset-backed securities. (c) In the second quarter of 2018, Evergy and Westar Energy re-evaluated the classification, within the fair value hierarchy, of their various fund investments within both Westar Energy's nuclear decommissioning trust and rabbi trusts. As a result, Evergy and Westar Energy determined that certain fund investments within the nuclear decommissioning trust in the amount of $199.4 million as of December 31, 2017, should have been classified as Level 1, instead of Level 2. This determination is based on the fact that the fair value of these funds is based on daily published prices at which Evergy and Westar Energy are able to redeem their investments without restriction on a daily basis. Evergy and Westar Energy also determined that certain fund investments within their rabbi trusts in the amount of $34.1 million as of December 31, 2017, should have been measured using the NAV per share (or its equivalent) practical expedient, instead of as a Level 2 investment. This determination is based on the fact that these funds do not meet the definition of readily determinable fair value due to the absence of a published NAV. Evergy and Westar Energy have determined that these errors are immaterial to their current and previously filed financial reports and accordingly, have not revised prior periods but have reflected the changes in fair value hierarchy classification as of December 31, 2018. (d) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.
Fair value investments, entities that calculate NAV	The following table provides additional information on these Evergy and Westar Energy investments. December 31, 2018 December 31, 2017 December 31, 2018 Fair Unfunded Fair Unfunded Redemption Length of Value Commitments Value Commitments Frequency Settlement Westar Energy (millions) Nuclear decommissioning trust: Domestic equity funds $ 6.7 $ 4.3 $ 5.1 $ 2.8 (a) (a) Alternative investments fund (b) 24.1 — 21.7 — Quarterly 65 days Real estate securities fund (b) 11.8 — 10.8 — Quarterly 65 days Total $ 42.6 $ 4.3 $ 37.6 $ 2.8 Rabbi trust: Core bond fund $ 24.8 $ — $ — $ — (c) (c) Combination debt/equity/other fund 5.6 — — — (c) (c) Total $ 30.4 $ — $ — $ — Other Evergy Rabbi trusts: Fixed income fund (d) $ 13.2 $ — $ — $ — (c) (c) Total Evergy investments at NAV $ 86.2 $ 4.3 $ 37.6 $ 2.8 (a) This investment is in five long-term private equity funds that do not permit early withdrawal. Investments in these funds cannot be distributed until the underlying investments have been liquidated, which may take years from the date of initial liquidation. Three funds have begun to make distributions. The initial investment in the fourth and fifth fund occurred in the second quarter of 2016 and first quarter of 2018, respectively. The fourth fund's term is 15 years , subject to the general partner's right to extend the term for up to three additional one -year periods. The fifth fund's term will be 15 years after the initial closing date, subject to additional extensions approved by the Advisory Committee to provide for an orderly liquidation of fund investments and dissolution of the fund. (b) There is a holdback on final redemptions. (c) This investment can be redeemed immediately and is not subject to any restrictions on redemptions. (d) This investment is recorded at GMO. GMO amounts are not included in consolidated Evergy as of December 31, 2017.
Fair value recurring gain (loss) included in earnings	The following table summarizes the net unrealized gains (losses) for the Evergy Companies' nuclear decommissioning trusts and rabbi trusts. 2018 2017 2016 Westar Energy (millions) Nuclear decommissioning trust - equity securities $ (31.8 ) $ 15.7 $ 9.0 Rabbi trust 1.0 (14.3 ) 1.4 Total $ (30.8 ) $ 1.4 $ 10.4 KCP&L (a) Nuclear decommissioning trust - equity securities $ (20.7 ) $ 26.7 $ 14.8 Nuclear decommissioning trust - debt securities (2.5 ) 0.5 (0.3 ) Total $ (23.2 ) $ 27.2 $ 14.5 Evergy Nuclear decommissioning trust - equity securities $ (54.1 ) $ 15.7 $ 9.0 Nuclear decommissioning trust - debt securities (0.5 ) — — Rabbi trusts 1.0 (14.3 ) 1.4 Total $ (53.6 ) $ 1.4 $ 10.4 (a) KCP&L amounts are only included in consolidated Evergy from the date of the merger, June 4, 2018 through December 31, 2018 .

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Leases [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	Total Operating Leases Evergy Westar Energy KCP&L (a) Rental expense: (millions) 2016 $ 13.6 $ 13.6 $ 13.7 2017 15.7 15.7 13.1 2018 24.5 17.7 11.4 Future commitments: 2019 $ 24.2 $ 14.0 $ 10.2 2020 20.7 10.1 10.6 2021 18.4 8.1 10.3 2022 15.2 5.2 10.0 2023 12.4 2.8 9.6 After 2023 95.0 3.1 91.8 Total $ 185.9 $ 43.3 $ 142.5
Schedule of Capital Leased Assets [Table Text Block]	December 31 2018 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (a) (millions) Vehicles $ 20.2 $ 20.2 $ — $ 19.7 $ 19.7 $ — Computer equipment 0.2 0.2 — 0.9 0.9 — Generation plant 296.7 40.1 — 40.1 40.1 — Other 5.2 — 2.6 — — 2.6 Accumulated amortization (160.0 ) (20.3 ) (1.1 ) (17.1 ) (17.1 ) (1.1 ) Total capital leases $ 162.3 $ 40.2 $ 1.5 $ 43.6 $ 43.6 $ 1.5
Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block]	Total Capital Leases Evergy Westar Energy KCP&L (millions) 2019 $ 6.4 $ 6.0 $ 0.2 2020 5.8 5.4 0.2 2021 5.3 4.9 0.2 2022 4.7 4.3 0.2 2023 4.0 3.6 0.2 After 2023 48.6 46.4 1.1 Total capital lease payments 74.8 70.6 2.1 Amounts representing imputed interest (25.8 ) (24.6 ) (0.6 ) Present value of net minimum lease payments under capital leases 49.0 46.0 1.5 Less: current portion (3.9 ) (3.7 ) (0.1 ) Total long-term obligations under capital leases $ 45.1 $ 42.3 $ 1.4
Contractual Obligation, Fiscal Year Maturity Schedule [Table Text Block]	Contractual Commitments - Fuel, Power and Other The Evergy Companies' contractual commitments at December 31, 2018 , excluding pensions, long-term debt and leases, are detailed in the following tables. Evergy 2019 2020 2021 2022 2023 After 2023 Total Purchase commitments (millions) Fuel $ 423.6 $ 364.4 $ 95.3 $ 82.9 $ 87.5 $ 116.2 $ 1,169.9 Power 47.3 47.3 47.4 47.6 47.8 366.8 604.2 Other 137.8 18.8 13.4 6.8 2.1 34.4 213.3 Total contractual commitments $ 608.7 $ 430.5 $ 156.1 $ 137.3 $ 137.4 $ 517.4 $ 1,987.4 Westar Energy 2019 2020 2021 2022 2023 After 2023 Total Purchase commitments (millions) Fuel $ 240.9 $ 218.1 $ 25.9 $ 45.7 $ 46.9 $ 74.1 $ 651.6 Other 87.4 8.9 5.5 2.2 — — 104.0 Total contractual commitments $ 328.3 $ 227.0 $ 31.4 $ 47.9 $ 46.9 $ 74.1 $ 755.6 KCP&L 2019 2020 2021 2022 2023 After 2023 Total Purchase commitments (millions) Fuel $ 162.6 $ 126.9 $ 69.4 $ 37.2 $ 40.6 $ 42.1 $ 478.8 Power 34.8 34.8 34.9 35.1 35.3 254.5 429.4 Other 34.7 9.0 7.0 3.8 1.6 29.7 85.8 Total contractual commitments $ 232.1 $ 170.7 $ 111.3 $ 76.1 $ 77.5 $ 326.3 $ 994.0

Related Party Transactions an_2

Related Party Transactions and Relationships (Tables)	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Schedule of related party receivables and payables	The following table summarizes Westar Energy's and KCP&L's related party net receivables and payables. December 31 2018 2017 Westar Energy (millions) Net receivable from GMO $ 2.6 $ — Net payable to KCP&L (13.5 ) — Net payable to Evergy (1.4 ) — KCP&L Net receivable from GMO $ 72.6 $ 65.8 Net receivable from Westar Energy 13.5 — Net receivable from Evergy 15.7 — Net receivable from Great Plains Energy — 18.9

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Variable Interest Entities	The following table summarizes the assets and liabilities related to the VIE described above that are recorded on Evergy's and Westar Energy's consolidated balance sheets. December 31 2018 2017 Assets: (millions) Property, plant and equipment of variable interest entities, net $ 169.2 $ 176.3 Liabilities: Current maturities of long-term debt of variable interest entities $ 30.3 $ 28.5 Accrued interest (a) 0.5 0.7 Long-term debt of variable interest entities, net 51.1 81.4 (a) Included in accrued interest on Evergy's and Westar Energy's consolidated balance sheets.

Taxes (Tables)

Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Summary of Tax Credit Carryforwards [Table Text Block]	Amount of Benefit Year of Origin Evergy Westar Energy KCP&L (millions) 2000 $ 7.3 $ 7.3 $ — 2001 9.8 9.7 — 2002 0.3 0.2 — 2003 0.3 0.2 — 2004 0.3 0.2 — 2005 0.3 0.2 — 2006 0.3 0.2 — 2007 0.6 0.5 — 2008 39.8 0.5 38.9 2009 47.7 0.2 47.4 2010 18.3 — 18.2 2011 13.3 — 13.2 2012 13.7 2.9 10.7 2013 23.5 10.5 12.9 2014 23.6 10.2 13.0 2015 23.5 10.1 12.8 2016 26.1 10.1 12.4 2017 43.3 34.5 8.2 2018 41.8 36.5 5.1 $ 333.8 $ 134.0 $ 192.8
Summary of Operating Loss Carryforwards [Table Text Block]	The year of origin of Evergy's, Westar Energy's and KCP&L's related tax benefit amounts for federal NOL carryforwards as of December 31, 2018 are detailed in the following table. Amount of Benefit Year of Origin Evergy Westar Energy KCP&L (millions) 2004 $ 1.6 $ — $ — 2005 44.4 — — 2006 32.0 — — 2009 21.9 — — 2010 2.5 — — 2011 65.3 — 38.4 2012 0.2 0.2 — 2013 1.5 0.8 0.3 2014 77.2 25.0 12.3 2015 59.3 0.2 55.6 2016 0.8 0.4 0.3 2017 16.2 12.3 0.6 2018 1.3 1.2 — $ 324.2 $ 40.1 $ 107.5
Schedule of Components of Income Tax Expense (Benefit)	Components of income tax expense are detailed in the following tables. Evergy 2018 2017 2016 Current income taxes (millions) Federal $ (67.4 ) $ 0.1 $ (1.0 ) State 2.2 0.4 0.3 Total (65.2 ) 0.5 (0.7 ) Deferred income taxes Federal 160.1 122.8 155.2 State (32.3 ) 30.7 32.9 Total 127.8 153.5 188.1 Investment tax credit Amortization (3.6 ) (2.8 ) (2.9 ) Total (3.6 ) (2.8 ) (2.9 ) Income tax expense $ 59.0 $ 151.2 $ 184.5 Westar Energy 2018 2017 2016 Current income taxes (millions) Federal $ (0.3 ) $ 0.1 $ (1.0 ) State (1.8 ) 0.4 0.3 Total (2.1 ) 0.5 (0.7 ) Deferred income taxes Federal 43.5 122.8 155.2 State (42.9 ) 30.7 32.9 Total 0.6 153.5 188.1 Investment tax credit Amortization (2.8 ) (2.8 ) (2.9 ) Total (2.8 ) (2.8 ) (2.9 ) Income tax expense (benefit) $ (4.3 ) $ 151.2 $ 184.5 KCP&L 2018 2017 2016 Current income taxes (millions) Federal $ 29.8 $ 37.4 $ 24.8 State 8.9 8.3 4.7 Total 38.7 45.7 29.5 Deferred income taxes Federal (3.4 ) 74.7 76.4 State 53.0 8.8 17.0 Total 49.6 83.5 93.4 Investment tax credit Amortization (1.0 ) (1.0 ) (1.0 ) Total (1.0 ) (1.0 ) (1.0 ) Income tax expense $ 87.3 $ 128.2 $ 121.9
Schedule of Effective Income Tax Rate Reconciliation	Effective Income Tax Rates Effective income tax rates reflected in the financial statements and the reasons for their differences from the statutory federal rates are detailed in the following tables. Evergy 2018 2017 2016 Federal statutory income tax 21.0 % 35.0 % 35.0 % COLI policies (1.9 ) (3.1 ) (4.2 ) State income taxes 4.9 4.1 4.0 Flow through depreciation for plant-related differences 0.8 2.3 3.1 Federal tax credits (6.4 ) (6.9 ) (1.8 ) Non-controlling interest (0.4 ) (0.9 ) (0.9 ) AFUDC equity (0.1 ) (0.2 ) (0.8 ) Amortization of federal investment tax credits (0.6 ) (0.6 ) (0.5 ) Changes in uncertain tax positions, net 0.1 — — Federal or state tax rate change (8.7 ) 2.5 — Valuation allowance 0.4 0.3 0.4 Stock compensation (0.4 ) (0.9 ) (0.5 ) Officer compensation limitation 1.2 0.2 — Other (0.2 ) (0.8 ) — Effective income tax rate 9.7 % 31.0 % 33.8 % Westar Energy 2018 2017 2016 Federal statutory income tax 21.0 % 35.0 % 35.0 % COLI policies (3.3 ) (3.1 ) (4.2 ) State income taxes 5.0 4.1 4.0 Flow through depreciation for plant-related differences 1.6 2.3 3.1 Federal tax credits (10.4 ) (6.9 ) (1.8 ) Non-controlling interest (0.6 ) (0.9 ) (0.9 ) AFUDC equity (0.2 ) (0.2 ) (0.8 ) Amortization of federal investment tax credits (0.8 ) (0.6 ) (0.5 ) Changes in uncertain tax positions, net 0.1 — — Federal or state tax rate change (15.3 ) 2.5 — Valuation allowance 0.5 0.3 0.4 Stock compensation (0.8 ) (0.9 ) (0.5 ) Officer compensation limitation 1.8 0.2 — Other 0.2 (0.8 ) — Effective income tax rate (1.2 )% 31.0 % 33.8 % KCP&L 2018 2017 2016 Federal statutory income tax 21.0 % 35.0 % 35.0 % COLI policies (0.2 ) (0.3 ) (0.2 ) State income taxes 5.5 3.8 4.1 Flow through depreciation for plant-related differences (2.5 ) 0.5 0.3 Federal tax credits (2.1 ) (2.4 ) (3.1 ) AFUDC equity (0.1 ) (0.7 ) (0.7 ) Amortization of federal investment tax credits (0.4 ) (0.3 ) (0.3 ) Federal or state tax rate change 14.1 5.3 — Valuation allowance — 0.4 — Stock compensation — 0.2 — Officer compensation limitation 0.6 0.1 0.2 Other (1.0 ) — (0.1 ) Effective income tax rate 34.9 % 41.6 % 35.2 %
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	Deferred Income Taxes The tax effects of major temporary differences resulting in deferred income tax assets (liabilities) in the consolidated balance sheets is in the following table. December 31 2018 2017 Evergy Westar Energy KCP&L Evergy Westar Energy KCP&L (a) Deferred tax assets: (millions) Tax credit carryforward $ 508.1 $ 307.1 $ 194.0 $ 276.7 $ 276.7 $ 185.8 Income taxes refundable to customers, net 478.1 233.1 186.9 230.3 230.3 179.1 Deferred employee benefit costs 215.4 89.6 118.3 95.9 95.9 124.6 Net operating loss carryforward 383.3 60.7 119.2 70.0 70.0 131.2 Deferred state income taxes 62.5 62.5 — 63.8 63.8 — Alternative minimum tax carryforward 73.4 26.7 — 52.2 52.2 — Accrued liabilities 82.6 13.6 32.8 13.2 13.2 26.0 Other 193.5 101.7 46.7 97.9 97.9 35.7 Total deferred tax assets before valuation allowance 1,996.9 895.0 697.9 900.0 900.0 682.4 Valuation allowances (27.3 ) (1.7 ) — — — — Total deferred tax assets, net 1,969.6 893.3 697.9 900.0 900.0 682.4 Deferred tax liabilities: Plant-related (3,164.9 ) (1,491.6 ) (1,199.7 ) (1,483.3 ) (1,483.3 ) (1,127.0 ) Deferred employee benefit costs (199.9 ) (89.6 ) (86.1 ) (95.9 ) (95.9 ) (96.0 ) Acquisition premium (72.6 ) (72.6 ) — (76.6 ) (76.6 ) — Other (131.4 ) (54.9 ) (43.9 ) (59.9 ) (59.9 ) (75.5 ) Total deferred tax liabilities (3,568.8 ) (1,708.7 ) (1,329.7 ) (1,715.7 ) (1,715.7 ) (1,298.5 ) Net deferred income tax liabilities $ (1,599.2 ) $ (815.4 ) $ (631.8 ) $ (815.7 ) $ (815.7 ) $ (616.1 ) (a) KCP&L amounts are not included in consolidated Evergy at December 31, 2017.

Quarterly Operating Results (_2

Quarterly Operating Results (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]	20. QUARTERLY OPERATING RESULTS (UNAUDITED) Quarter Evergy 1st 2nd 3rd 4th 2018 (millions, except per share amounts) Operating revenue $ 600.2 $ 893.4 $ 1,582.5 $ 1,199.8 Operating income 123.5 126.9 533.1 150.1 Net income 62.9 104.4 357.6 21.1 Net income attributable to Evergy, Inc. 60.5 101.8 355.0 18.5 Basic and diluted earnings per common share 0.42 0.56 1.32 0.07 2017 Operating revenue $ 572.6 $ 609.3 $ 794.3 $ 594.8 Operating income 131.4 160.2 264.9 122.3 Net income 63.5 76.0 160.7 36.3 Net income attributable to Evergy, Inc. 59.7 72.1 158.3 33.8 Basic and diluted earnings per common share 0.42 0.50 1.11 0.24 Quarter Westar Energy 1st 2nd 3rd 4th 2018 (millions) Operating revenue $ 600.2 $ 650.9 $ 764.8 $ 599.0 Operating income 123.5 76.1 256.9 94.0 Net income 62.9 77.6 178.0 30.6 Net income attributable to Westar Energy, Inc. 60.5 75.0 175.4 28.0 2017 Operating revenue $ 572.6 $ 609.3 $ 794.3 $ 594.8 Operating income 131.4 160.2 264.9 122.3 Net income 63.5 76.0 160.7 36.3 Net income attributable to Westar Energy, Inc. 59.7 72.1 158.3 33.8 Quarter KCP&L 1st 2nd 3rd 4th 2018 (millions) Operating revenue $ 397.1 $ 452.2 $ 559.6 $ 414.2 Operating income 61.0 114.7 189.4 44.7 Net income (loss) 20.2 24.6 120.3 (2.2 ) 2017 Operating revenue $ 395.9 $ 482.7 $ 595.7 $ 416.4 Operating income 65.0 126.2 219.8 75.4 Net income 14.2 49.6 114.1 1.9 Quarterly data is subject to seasonal fluctuations with peak periods occurring in the summer months. Evergy's results reflect the results of operations of Westar Energy for all periods in 2017. Evergy had separate operations and includes the results of operation of KCP&L and GMO beginning with the quarter ended June 30, 2018. See Note 1 for more information.

Summary of Significant Accoun_4

Summary of Significant Accounting Policies Organization (Details) $ / shares in Units, customer in Millions, $ in Millions	Feb. 28, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)customersubsidiary$ / sharesRateMW	Dec. 31, 2017USD ($)$ / shares	Dec. 31, 2016$ / shares
Summary Of Accounting Policies [Line Items]
Pension and postretirement liability		$ 987.6	$ 491.2
Owned generating capacity and renewable purchased power | MW		14,500
Number of customers served | customer		1.6
Common Stock, Dividends, Per Share, Declared | $ / shares		$ 1.735	$ 1.60	$ 1.52
Goodwill		$ 2,338.9	$ 0
Westar Energy Inc [Member]
Summary Of Accounting Policies [Line Items]
Pension and postretirement liability		474.7	491.2
Westar Energy Inc [Member] | Restatement Adjustment [Member]
Summary Of Accounting Policies [Line Items]
Pension and postretirement liability		(50.2)
KCPL [Member]
Summary Of Accounting Policies [Line Items]
Pension and postretirement liability		$ 491.9	$ 512.2
Kansas Gas And Electric Company [Member] | Westar Energy Inc [Member]
Summary Of Accounting Policies [Line Items]
Number of active wholly owned subsidiaries | subsidiary		1
Prairie Wind Transmission, LLC [Member] | Westar Energy Inc [Member]
Summary Of Accounting Policies [Line Items]
Ownership percentage | Rate		50.00%
Transource Energy, LLC [Member] | AEP Transmission Holding Company, LLC [Member]
Summary Of Accounting Policies [Line Items]
Ownership interest | Rate		86.50%
Transource Energy, LLC [Member] | GPE Transmission Holding Company, LLC [Member]
Summary Of Accounting Policies [Line Items]
Ownership percentage | Rate		13.50%
Subsequent Event [Member] | Westar Energy Inc [Member]
Summary Of Accounting Policies [Line Items]
Dividends Payable	$ 110
Subsequent Event [Member] | Common Stock [Member]
Summary Of Accounting Policies [Line Items]
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.475

Summary of Significant Accoun_5

Summary of Significant Accounting Policies Summary of Reclassifications (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Amortization of deferred refueling outage	$ 21.2	$ 16.1	$ 18.4
Deferred income taxes, net	127.8	153.5	188.1
Investment tax credit amortization	(3.6)	(2.8)	(2.9)
Net deferred income taxes and credits	124.2	149.6	185.2
Other/Solar rebates paid	(2)	(6)	(22)
Fuel inventory and supplies	54.7	7.2	1.8
Prepaid expenses and other current assets	(128.1)	55.8	(18.3)
Other current liabilities	92	(118)	(86.4)
Changes in other assets	66.8	32	21.4
Changes in other liabilities	(15.9)	19.3	23.3
Total reclassifications	1,497.8	912.7	803.8
Additions to property, plant and equipment	(1,069.7)	(764.6)	(1,087)
Allowance for borrowed funds used during construction	(10.4)	(5.6)	(10)
Other investing activities	(17.6)	(3.6)	(4.1)
Total reclassifications	197.4	(780.8)	(994.1)
Westar Energy Inc [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Amortization of deferred refueling outage	13.7	16.1	18.4
Deferred income taxes, net	0.6	153.5	188.1
Investment tax credit amortization	(2.8)	(2.8)	(2.9)
Net deferred income taxes and credits	(2.2)	149.6	185.2
Other/Solar rebates paid	(2.2)	(6)	(22)
Fuel inventory and supplies	17.3	7.2	1.8
Prepaid expenses and other current assets	(134.2)	55.8	(18.3)
Other current liabilities	88.3	(118)	(86.4)
Changes in other assets	42.7	32	21.4
Changes in other liabilities	(36.2)	19.3	23.3
Total reclassifications	751.9	912.7	803.8
Additions to property, plant and equipment	(713.3)	(764.6)	(1,087)
Allowance for borrowed funds used during construction	(6.6)	(5.6)	(10)
Other investing activities	(8.6)	(3.6)	(4.1)
Total reclassifications	(727.4)	(780.8)	(994.1)
KCPL [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Amortization of deferred refueling outage	13.5	18.3	19
Deferred income taxes, net	49.6	83.5	93.4
Investment tax credit amortization	(1)	(1)	(1)
Net deferred income taxes and credits	48.6	82.5	92.4
Other/Solar rebates paid	3.9	7.5	8.8
Fuel inventory and supplies	19.4	(5.2)	6.3
Prepaid expenses and other current assets	7.2	8.4	(73.2)
Other current liabilities	10.4	(0.1)	10.4
Changes in other assets	42.9	31.7	66.5
Changes in other liabilities	37.9	6.5	(9.4)
Total reclassifications	657.7	610.9	623.3
Additions to property, plant and equipment	(430.7)	(468.6)	(447.9)
Allowance for borrowed funds used during construction	(4.9)	(6.1)	(5.6)
Other investing activities	4.8	0.9	(0.3)
Total reclassifications	$ (433.9)	(471)	(451.5)
KCPL [Member] | As Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Amortization of other		30.2	33.9
Amortization of deferred refueling outage		0	0
Deferred income taxes, net		83.5	93.4
Investment tax credit amortization		(1)	(1)
Net deferred income taxes and credits		0	0
Payments for asset retirement obligations		(25.5)	0
Other/Solar rebates paid		(9)	1.4
Fuel inventory and supplies		0	0
Fuel inventories		1.9	10.6
Materials and supplies		(7.1)	(4.3)
Prepaid expenses and other current assets		0	0
Other current liabilities		0	0
Changes in other assets		0	0
Changes in other liabilities		0	0
Deferred refueling outage costs		15.5	(3.1)
Pension and post-retirement benefit obligations		27.3	28.6
Fuel recovery mechanisms		8.3	(53.7)
Total reclassifications		124.1	105.8
Additions to property, plant and equipment		0	0
Utility capital expenditures		(437.7)	(418.8)
Allowance for borrowed funds used during construction		(6.1)	(5.6)
Other investing activities		(23.9)	(23.8)
Total reclassifications		(467.7)	(448.2)
KCPL [Member] | Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Amortization of other		0	0
Amortization of deferred refueling outage		18.3	19
Deferred income taxes, net		0	0
Investment tax credit amortization		0	0
Net deferred income taxes and credits		82.5	92.4
Payments for asset retirement obligations		(25.5)	(15)
Other/Solar rebates paid		7.5	8.8
Fuel inventory and supplies		(5.2)	6.3
Fuel inventories		0	0
Materials and supplies		0	0
Prepaid expenses and other current assets		8.4	(73.2)
Other current liabilities		(0.1)	10.4
Changes in other assets		31.7	66.5
Changes in other liabilities		6.5	(9.4)
Deferred refueling outage costs		0	0
Pension and post-retirement benefit obligations		0	0
Fuel recovery mechanisms		0	0
Total reclassifications		124.1	105.8
Additions to property, plant and equipment		(468.6)	(447.9)
Utility capital expenditures		0	0
Allowance for borrowed funds used during construction		0	0
Other investing activities		0.9	(0.3)
Total reclassifications		$ (467.7)	$ (448.2)

Summary of Significant Accoun_6

Summary of Significant Accounting Policies Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash paid for (received from):
Interest, net of amounts capitalized	$ 255.9	$ 153.9	$ 139
Income taxes, net of refunds	(0.9)	(12.7)	13.1
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	(7.8)	158.8	151.5
Deconsolidation of property, plant and equipment of VIE	0	(72.9)	0
Non-cash financing transactions:
Issuance of stock for compensation and reinvested dividends	0.5	5.1	9.7
Non-cash financing, deconsolidation of VIE	0	(83.1)	0
Assets acquired through capital leases	1.2	4.8	2.7
KCPL [Member]
Cash paid for (received from):
Interest, net of amounts capitalized	129.4	128	127
Income taxes, net of refunds	31.2	38.8	(37.3)
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	19.2	36.6	75.4
Westar Energy Inc [Member]
Cash paid for (received from):
Interest, net of amounts capitalized	155.3	153.9	139
Income taxes, net of refunds	37.5	(12.7)	13.1
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	(32.5)	158.8	151.5
Deconsolidation of property, plant and equipment of VIE	0	(72.9)	0
Non-cash financing transactions:
Issuance of stock for compensation and reinvested dividends	0	5.1	9.7
Non-cash financing, deconsolidation of VIE	0	(83.1)	0
Assets acquired through capital leases	1.2	4.8	2.7
Variable Interest Entities [Member]
Cash paid for (received from):
Interest, net of amounts capitalized	2.3	3.1	5.8
Variable Interest Entities [Member] | Westar Energy Inc [Member]
Cash paid for (received from):
Interest, net of amounts capitalized	$ 2.3	$ 3.1	$ 5.8

Summary of Significant Accoun_7

Summary of Significant Accounting Policies Fuel Inventory and Supplies (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Inventory [Line Items]
Fuel inventory	$ 168.9	$ 94.1
Supplies	342.1	199.5
Fuel inventory and supplies	511	293.6
KCPL [Member]
Inventory [Line Items]
Fuel inventory	57.8	71
Supplies	119.8	126
Fuel inventory and supplies	177.6	197
Westar Energy Inc [Member]
Inventory [Line Items]
Fuel inventory	87.8	94.1
Supplies	189	199.5
Fuel inventory and supplies	$ 276.8	$ 293.6

Summary of Significant Accoun_8

Summary of Significant Accounting Policies Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Regulatory Assets	$ 2,061.8	$ 784.9
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	3.00%
Minimum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	8 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	15 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	8 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	5 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	87 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	94 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	73 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	84 years
Westar Energy Inc [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets	$ 797.5	784.9
Westar Energy Inc [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	8 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	36 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	19 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	7 years
Westar Energy Inc [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	87 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	94 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	73 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	84 years
KCPL [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets	$ 626.1	698.7
KCPL [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	20 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	15 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	8 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	5 years
KCPL [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	60 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	70 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	55 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	50 years
Retired Generation Facility [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets	$ 159.9	0
Retired Generation Facility [Member] | Westar Energy Inc [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets	0	0
Retired Generation Facility [Member] | KCPL [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets	$ 0	$ 0

Summary of Significant Accoun_9

Summary of Significant Accounting Policies Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest									$ 546	$ 336.5	$ 361.2
Less: Net income attributable to noncontrolling interests									10.2	12.6	14.6
Net Income (Loss) Attributable to Parent	$ 18.5	$ 355	$ 101.8	$ 60.5	$ 33.8	$ 158.3	$ 72.1	$ 59.7	$ 535.8	$ 323.9	$ 346.6
Weighted Average Number of Shares Outstanding, Basic									213,900,000	142,500,000	142,100,000
Weighted Average Number Diluted Shares Outstanding Adjustment									200,000	100,000	400,000
Weighted Average Number of Shares Outstanding, Diluted									214,100,000	142,600,000	142,500,000
Earnings Per Share, Basic and Diluted	$ 0.07	$ 1.32	$ 0.56	$ 0.42	$ 0.24	$ 1.11	$ 0.50	$ 0.42	$ 2.50	$ 2.27	$ 2.43
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									0	0	0

Summary of Significant Accou_10

Summary of Significant Accounting Policies Allowance For Funds Used During Construction (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
AFUDC borrowed funds	$ 10.4	$ 5.6	$ 10
AFUDC equity funds	3.1	2	11.6
Total	$ 13.5	$ 7.6	$ 21.6
Westar Energy Inc [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate	3.30%	2.30%	4.20%
AFUDC borrowed funds	$ 6.6	$ 5.6	$ 10
AFUDC equity funds	2.9	2	11.6
Total	$ 9.5	$ 7.6	$ 21.6
KCPL [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate	3.90%	4.90%	5.70%
AFUDC borrowed funds	$ 4.9	$ 6.1	$ 5.6
AFUDC equity funds	1.4	6	6.6
Total	$ 6.3	$ 12.1	$ 12.2
Kcpl Greater Missouri Operations Member
Property, Plant and Equipment [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate	2.90%	1.90%	1.60%

Summary of Significant Accou_11

Summary of Significant Accounting Policies Corporate-Owned Life Insurance (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Corporate-Owned Life Insurance [Abstract]
Cash surrender value of policies	$ 1,441.7	$ 1,320.7
Borrowings against policies	(1,306.9)	(1,189.2)
Corporate-owned life insurance, net	$ 134.8	$ 131.5

Summary of Significant Accou_12

Summary of Significant Accounting Policies Other Income (Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Non Service Cost Component Of Net Benefit Cost	$ (47.8)	$ (20)	$ (20.6)
Other	(30.9)	(19.1)	(18)
Other expense	78.7	39.1	38.6
Westar Energy Inc [Member]
Non Service Cost Component Of Net Benefit Cost	(23.5)	(20)	(20.6)
Other	(23.3)	(19.1)	(18)
Other expense	46.8	39.1	38.6
KCPL [Member]
Non Service Cost Component Of Net Benefit Cost	(25.9)	(42.7)	(37.2)
Other	(5)	(8.1)	(7.6)
Other expense	$ 30.9	$ 50.8	$ 44.8

Summary of Significant Accou_13

Summary of Significant Accounting Policies New Accounting Standards (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Of Accounting Policies [Line Items]
Net Cash Provided by (Used in) Operating Activities										$ 1,497.8	$ 912.7	$ 803.8
Net Cash Provided by (Used in) Investing Activities										197.4	(780.8)	(994.1)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		$ 160.3				$ 3.5				160.3	3.5	3.2	$ 3.3
Taxes other than income tax										269.1	167.6	191.7
Revenues		1,199.8	$ 1,582.5	$ 893.4	$ 600.2	594.8	$ 794.3	$ 609.3	$ 572.6	4,275.9	2,571	2,562.1
Westar Energy Inc [Member]
Summary Of Accounting Policies [Line Items]
Net Cash Provided by (Used in) Operating Activities										751.9	912.7	803.8
Net Cash Provided by (Used in) Investing Activities										(727.4)	(780.8)	(994.1)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		44.5				3.5				44.5	3.5	3.2	3.3
Taxes other than income tax										173.7	167.6	191.7
Revenues		599	764.8	650.9	600.2	594.8	794.3	609.3	572.6	2,614.9	2,571	2,562.1
KCPL [Member]
Summary Of Accounting Policies [Line Items]
Net Cash Provided by (Used in) Operating Activities										657.7	610.9	623.3
Net Cash Provided by (Used in) Investing Activities										(433.9)	(471)	(451.5)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		2.6				2.2				2.6	2.2	4.5	$ 2.3
Taxes other than income tax										117.2	182.5	177.5
Revenues		$ 414.2	$ 559.6	$ 452.2	$ 397.1	416.4	$ 595.7	$ 482.7	$ 395.9	1,823.1	1,890.7	1,875.4
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | KCPL [Member]
Summary Of Accounting Policies [Line Items]
Taxes other than income tax										76.4
Revenues										$ 76.4
Accounting Standards Update 2016-15 - Corporate Owned Life Insurance, Settlements [Member]
Summary Of Accounting Policies [Line Items]
Net Cash Provided by (Used in) Operating Activities											(2.8)	(22.1)
Net Cash Provided by (Used in) Investing Activities											2.8	22.1
Accounting Standards Update 2016-15 - Corporate Owned Life Insurance, Premiums [Member]
Summary Of Accounting Policies [Line Items]
Net Cash Provided by (Used in) Operating Activities											3.1	3.4
Net Cash Provided by (Used in) Investing Activities											(3.1)	(3.4)
Accounting Standards Update 2016-18 [Member]
Summary Of Accounting Policies [Line Items]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents						$ 0.1					$ 0.1	$ 0.1
Accounting Standards Update 2016-02 [Member] | Subsequent Event [Member]
Summary Of Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 110
Accounting Standards Update 2016-02 [Member] | Westar Energy Inc [Member] | Subsequent Event [Member]
Summary Of Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	40
Accounting Standards Update 2016-02 [Member] | KCPL [Member] | Subsequent Event [Member]
Summary Of Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 80

Summary of Significant Accou_14

Summary of Significant Accounting Policies Schedule of Retrospective Adjustments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense									$ 1,115.8	$ 563.5	$ 587.2
Total operating expenses									3,342.3	1,892.2	1,859.7
Income from operations	$ 150.1	$ 533.1	$ 126.9	$ 123.5	$ 122.3	$ 264.9	$ 160.2	$ 131.4	933.6	678.8	702.4
Other expense									(78.7)	(39.1)	(38.6)
Total other income (expense), net									(54.4)	(26.8)	(1.5)
As Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense										583.5	607.8
Total operating expenses										1,912.2	1,880.3
Income from operations										658.8	681.8
Other expense										(19.1)	(18)
Total other income (expense), net										(6.8)	19.1
Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense										563.5	587.2
Total operating expenses										1,892.2	1,859.7
Income from operations										678.8	702.4
Other expense										(39.1)	(38.6)
Total other income (expense), net										(26.8)	(1.5)
Accounting Standards Update 2017-07 [Member] | Scenario, Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense										(20)	(20.6)
Total operating expenses										(20)	(20.6)
Income from operations										20	20.6
Other expense										(20)	(20.6)
Total other income (expense), net										(20)	(20.6)
Westar Energy Inc [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense									640.7	563.5	587.2
Total operating expenses									2,064.4	1,892.2	1,859.7
Income from operations	94	256.9	76.1	123.5	122.3	264.9	160.2	131.4	550.5	678.8	702.4
Other expense									(46.8)	(39.1)	(38.6)
Total other income (expense), net									(33.5)	(26.8)	(1.5)
Westar Energy Inc [Member] | As Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense										583.5	607.8
Total operating expenses										1,912.2	1,880.3
Income from operations										658.8	681.8
Other expense										(19.1)	(18)
Total other income (expense), net										(6.8)	19.1
Westar Energy Inc [Member] | Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense										563.5	587.2
Total operating expenses										1,892.2	1,859.7
Income from operations										678.8	702.4
Other expense										(39.1)	(38.6)
Total other income (expense), net										(26.8)	(1.5)
Westar Energy Inc [Member] | Accounting Standards Update 2017-07 [Member] | Scenario, Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense										(20)	(20.6)
Total operating expenses										(20)	(20.6)
Income from operations										20	20.6
Other expense										(20)	(20.6)
Total other income (expense), net										(20)	(20.6)
KCPL [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense									494.2	474.8	502
Total operating expenses									1,413.3	1,404.3	1,356.1
Income from operations	$ 44.7	$ 189.4	$ 114.7	$ 61	$ 75.4	$ 219.8	$ 126.2	$ 65	409.8	486.4	519.3
Other expense									(30.9)	(50.8)	(44.8)
Total other income (expense), net									$ (25.9)	(39.6)	(33)
KCPL [Member] | As Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense										517.5	539.2
Total operating expenses										1,447	1,393.3
Income from operations										443.7	482.1
Other expense										(8.1)	(7.6)
Total other income (expense), net										3.1	4.2
KCPL [Member] | Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense										474.8	502
Total operating expenses										1,404.3	1,356.1
Income from operations										486.4	519.3
Other expense										(50.8)	(44.8)
Total other income (expense), net										(39.6)	(33)
KCPL [Member] | Accounting Standards Update 2017-07 [Member] | Scenario, Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating and maintenance expense										(42.7)	(37.2)
Total operating expenses										(42.7)	(37.2)
Income from operations										42.7	37.2
Other expense										(42.7)	(37.2)
Total other income (expense), net										$ (42.7)	$ (37.2)

Merger of Great Plains Energy_3

Merger of Great Plains Energy and Westar Energy - Narrative (Details) $ in Millions	Jun. 04, 2018	May 31, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Acquisition-related Costs [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
Merger-related, after tax costs			$ 74.7	$ 14.8
Merger Settlement Agreement [Member] | Kansas Corporation Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		$ 30.6
Additional bill credits		46
Additional bill credits, annual amount		11.5
Merger-related savings on current rate cases		$ 30
Base rate moratorium period		5 years
Return on equity refund		50.00%
Charitable contributions period		5 years
Merger transaction costs, recovery amount		$ 30.9
Merger transaction costs, recovery period		10 years
Merger Settlement Agreement [Member] | Missouri Public Service Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		$ 29.1
Charitable contributions period		5 years
Merger transaction costs, recovery amount		$ 16.9
Merger transaction costs, recovery period		10 years
One-time bill credits, period		120 days
Support to promote low-income weatherization, amount		$ 3
Support to promote low-income weatherization, period		10 years
Westar Energy Inc [Member] | Merger Settlement Agreement [Member] | Kansas Corporation Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		$ 23.1
Additional bill credits, annual amount		8.7
Merger-related savings on current rate cases		22.5
Merger transaction costs, recovery amount		23.2
KCPL [Member] | Merger Settlement Agreement [Member] | Kansas Corporation Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		7.5
Additional bill credits, annual amount		2.8
Merger-related savings on current rate cases		7.5
Merger transaction costs, recovery amount		7.7
KCPL [Member] | Merger Settlement Agreement [Member] | Missouri Public Service Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		14.9
Merger transaction costs, recovery amount		9.7
KCPL Greater Missouri Operations [Member] | Merger Settlement Agreement [Member] | Missouri Public Service Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		14.2
Merger transaction costs, recovery amount		$ 7.2
Westar Energy Inc [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
Conversion ratio	1
Great Plains Energy [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
Earnings or Loss of Acquiree since Acquisition Date, Actual			236.2
Conversion ratio	0.5981
Revenue of acquiree since acquisition			1,661.1
Merger-related costs			$ 148	$ 11.9

Merger of Great Plains Energy_4

Merger of Great Plains Energy and Westar Energy - Schedule of Pre-tax Costs and Deferrals (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2018	Dec. 31, 2018
Great Plains Energy [Member]
Business Acquisition [Line Items]
One-time bill credits		$ (59.7)
Annual bill credits		(10.5)
Total impact to operating revenues		(70.2)
Charitable contributions and community support		24.7
Voluntary severance and accelerated equity compensation		47.9
Other transaction and transition costs		51
Reallocation and deferral of merger transition costs		(47.8)
Total impact to operating and maintenance expense		75.8
Total		(146)
Westar Energy Inc [Member] | Great Plains Energy [Member]
Business Acquisition [Line Items]
One-time bill credits		(23.1)
Annual bill credits		(7.9)
Total impact to operating revenues		(31)
Charitable contributions and community support		0
Voluntary severance and accelerated equity compensation		44.2
Other transaction and transition costs		21.5
Reallocation and deferral of merger transition costs		(13.8)
Total impact to operating and maintenance expense		51.9
Total		(82.9)
KCPL [Member] | Great Plains Energy [Member]
Business Acquisition [Line Items]
One-time bill credits		(22.4)
Annual bill credits		(2.6)
Total impact to operating revenues		(25)
Charitable contributions and community support		0
Voluntary severance and accelerated equity compensation		2.6
Other transaction and transition costs		2.1
Reallocation and deferral of merger transition costs		(23.2)
Total impact to operating and maintenance expense		(18.5)
Total		$ (6.5)
Merger Settlement Agreement [Member] | Kansas Corporation Commission [Member]
Business Acquisition [Line Items]
Additional bill credits, annual amount	$ 11.5
Merger Settlement Agreement [Member] | Kansas Corporation Commission [Member] | Westar Energy Inc [Member]
Business Acquisition [Line Items]
Additional bill credits, annual amount	8.7
Merger Settlement Agreement [Member] | Kansas Corporation Commission [Member] | KCPL [Member]
Business Acquisition [Line Items]
Additional bill credits, annual amount	$ 2.8

Merger of Great Plains Energy_5

Merger of Great Plains Energy and Westar Energy - Purchase Price Allocation (Details) $ / shares in Units, $ in Millions	Jun. 04, 2018USD ($)$ / sharesshares
Business Acquisition [Line Items]
Common stock outstanding (in shares)	215,800,074
Awards outstanding (in shares)	(204,825)
Great Plains Energy shares to be converted to Evergy shares (in shares)	215,595,249
Great Plains Energy [Member]
Business Acquisition [Line Items]
Exchange ratio	0.5981
Number of shares issued (in shares)	128,947,518
Closing price (in dollars per share) | $ / shares	$ 54
Total purchase price | $	$ 6,975.7
Common Stock [Member] | Great Plains Energy [Member]
Business Acquisition [Line Items]
Fair value of shares issued | $	6,963.2
Stock Compensation Plan [Member] | Great Plains Energy [Member]
Business Acquisition [Line Items]
Fair value of shares issued | $	$ 12.5

Merger of Great Plains Energy_6

Merger of Great Plains Energy and Westar Energy - Schedule Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jun. 04, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 2,338.9		$ 0
Great Plains Energy [Member]
Business Acquisition [Line Items]
Current assets		$ 2,151.7
Property, plant and equipment, net		9,179.7
Goodwill		2,338.9
Other long-term assets, excluding goodwill		1,235.9
Total assets		14,906.2
Current liabilities		1,673.9
Long-term liabilities, excluding long-term debt		2,898
Long-term debt, net		3,358.6
Total liabilities		7,930.5
Total purchase price		$ 6,975.7

Merger of Great Plains Energy_7

Merger of Great Plains Energy and Westar Energy - Unaudited Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Great Plains Energy [Member]
Business Acquisition [Line Items]
Operating revenues	$ 5,334.6	$ 5,279.2
Net income attributable to Evergy, Inc.	$ 714.3	$ 468.9
Basic earnings per common share (in dollars per share)	$ 2.67	$ 1.73
Diluted earnings per common share (in dollars per share)	$ 2.67	$ 1.73
Acquisition-related Costs [Member]
Business Acquisition [Line Items]
Merger-related after-tax financing costs		$ 278
Merger contingent, after-tax mark-to-market interest rate swap gains	$ 36.6	7.3
Merger-related, after tax costs	74.7	$ 14.8
Merger-related, reductions of revenues for customer bill credits	$ 44.4

Revenue (Details)

Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									$ 4,224
Other									51.9
Revenues	$ 1,199.8	$ 1,582.5	$ 893.4	$ 600.2	$ 594.8	$ 794.3	$ 609.3	$ 572.6	4,275.9	$ 2,571	$ 2,562.1
Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									2,606.6
Other									8.3
Revenues	599	764.8	650.9	600.2	594.8	794.3	609.3	572.6	2,614.9	2,571	2,562.1
KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,752
Other									71.1
Revenues	$ 414.2	$ 559.6	$ 452.2	$ 397.1	$ 416.4	$ 595.7	$ 482.7	$ 395.9	1,823.1	$ 1,890.7	$ 1,875.4
Electric Utility Customer Class Residential [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,578.8
Electric Utility Customer Class Residential [Member] | Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									846.4
Electric Utility Customer Class Residential [Member] | KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									735.6
Electric Utility Customer Class Commercial [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,356.4
Electric Utility Customer Class Commercial [Member] | Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									702.8
Electric Utility Customer Class Commercial [Member] | KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									794.8
Electric Utility Customer Class Industrial [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									527.8
Electric Utility Customer Class Industrial [Member] | Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									396.4
Electric Utility Customer Class Industrial [Member] | KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									138.8
Electric Utility Customer Class Other Retail [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									30.6
Electric Utility Customer Class Other Retail [Member] | Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									20
Electric Utility Customer Class Other Retail [Member] | KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									10.4
Electric Utility Customer Class Total Electric Retail [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									3,493.6
Electric Utility Customer Class Total Electric Retail [Member] | Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,965.6
Electric Utility Customer Class Total Electric Retail [Member] | KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									1,679.6
Electric Utility Customer Class Wholesale [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									404.4
Electric Utility Customer Class Wholesale [Member] | Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									346.1
Electric Utility Customer Class Wholesale [Member] | KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									53.5
Electric Utility Customer Class Transmission [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									308.1
Electric Utility Customer Class Transmission [Member] | Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									288.9
Electric Utility Customer Class Transmission [Member] | KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									14.5
Electric Utility Customer Class Industrial Steam [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									17.9
Electric Utility Customer Class Industrial Steam [Member] | Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									6
Electric Utility Customer Class Industrial Steam [Member] | KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									$ 4.4

Receivables (Details)

Receivables (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	$ 95	$ 55.4
Allowance for doubtful accounts	(9.2)	(6.7)
Total	193.7	290.7
Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	71.6	55.4
Allowance for doubtful accounts	(3.9)	(6.7)
Total	84.3	290.7
KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	15.8	39.3
Allowance for doubtful accounts	(3.8)	(2.2)
Total	62.7	106.3
Trade Accounts Receivable [Member] | Billed Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	16.7	165.4
Trade Accounts Receivable [Member] | Billed Revenues [Member] | Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	0	165.4
Trade Accounts Receivable [Member] | Billed Revenues [Member] | KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	7.8	1.6
Trade Accounts Receivable [Member] | Unbilled Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	91.2	76.6
Trade Accounts Receivable [Member] | Unbilled Revenues [Member] | Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	16.6	76.6
Trade Accounts Receivable [Member] | Unbilled Revenues [Member] | KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	$ 42.9	$ 67.6

Receivables - Narrative (Detail

Receivables - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Other receivables, contracts with customers	$ 65.8
Sale Of Accounts Receivable - KCPL and GMO
Accounts receivable pledged as collateral	365	$ 0
Collateralized note payable	365	0
Westar Energy Inc [Member]
Other receivables, contracts with customers	55.9
Sale Of Accounts Receivable - KCPL and GMO
Accounts receivable pledged as collateral	185	0
Maximum Amount Of Outstanding Principal Under Receivables Agreement From Mid-Dec To Mid-Jan	185
Collateralized note payable	185	0
Maximum Amount Of Outstanding Principal Under Receivables Agreement From Jan To Mid Feb	125
Maximum amount of outstanding principal under receivable agreement from mid-July to expiration	200
Maximum Amount Of Outstanding Principal Under Receivables Agreement From Mid February to Mid July	185
KCPL [Member]
Other receivables, contracts with customers	5.5
Sale Of Accounts Receivable - KCPL and GMO
Accounts receivable pledged as collateral	130	130
Collateralized note payable	130	$ 130
Maximum amount of outstanding principal under receivables agreement	130
KCPL Greater Missouri Operations [Member]
Sale Of Accounts Receivable - KCPL and GMO
Maximum amount of outstanding principal under receivables agreement from mid-November to mid-June	50
Maximum amount of outstanding principal under receivables agreement from mid-June to expiration	$ 65

Receivables - Summary of Bad De

Receivables - Summary of Bad Debt Expense (Details) - SEC Schedule, 12-09, Allowance, Credit Loss [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment losses recognized on receivables	$ 20.7	$ 10.5	$ 12.2
Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment losses recognized on receivables	9	10.5	12.2
KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment losses recognized on receivables	13.1	7.5	6.4
Customer Contracts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment losses recognized on receivables	20.2	10.3	11.4
Customer Contracts [Member] | Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment losses recognized on receivables	8.5	10.3	11.4
Customer Contracts [Member] | KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment losses recognized on receivables	$ 13.1	$ 7.6	$ 6.3

Rate Matters and Regulation (De

Rate Matters and Regulation (Details) - USD ($) $ in Millions	1 Months Ended								12 Months Ended
	Jan. 31, 2019	Oct. 31, 2018	Sep. 30, 2018	Jul. 31, 2018	May 31, 2018	Mar. 31, 2018	Feb. 28, 2018	Jan. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Regulatory Proceedings [Line Items]
Regulatory Liabilities									$ 2,329	$ 1,105.6
Westar Energy Inc [Member]
Regulatory Proceedings [Line Items]
Regulatory Liabilities									1,121.3	1,105.6
KCPL [Member]
Regulatory Proceedings [Line Items]
Regulatory Liabilities									847.1	779.2
Transmission Delivery Charge [Member] | Westar Energy Inc [Member] | Kansas Corporation Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase (decrease), approved		$ (20)				$ 31.5
2018 Rate Case Proceedings [Member] | Westar Energy Inc [Member] | Kansas Corporation Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase (decrease), requested							$ (2)
Revised annual revenue increase, requested							$ 54
Return on equity, requested							9.85%
Return on equity, approved				9.30%
Rate-making equity ratio, requested							51.60%
Rate-making equity ratio, approved				51.46%
Annual revenue increase (decrease) related to rebasing, approved				$ 16
Increase (decrease) in depreciation expense, approved				46
Recovery of wholesale contract, approved				41
One-time bill credit, approved				50
Annual revenue increase (decrease), approved, not including rebasing				$ (66)
2018 Rate Case Proceedings [Member] | KCPL Greater Missouri Operations [Member] | Missouri Public Service Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase (decrease), approved			$ (24)
Return on equity, requested								9.85%
Rate-making equity ratio, requested								54.40%
Annual revenue increase (decrease) related to rebasing, requested								$ 21.7
One-time bill credit, approved			29.3
Final amount of one time customer bill credit			27.4
Annual revenue increase (decrease), requested, not including rebasing								$ (2.4)
2018 Rate Case Proceedings [Member] | KCPL [Member] | Missouri Public Service Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase (decrease), approved			(21.1)
Return on equity, requested								9.85%
Rate-making equity ratio, requested								50.03%
Annual revenue increase (decrease) related to rebasing, requested								$ 7.5
One-time bill credit, approved			38.7
Final amount of one time customer bill credit			$ 36.4
Annual revenue increase (decrease), requested, not including rebasing								$ 8.9
2018 Rate Case Proceedings [Member] | KCPL [Member] | Kansas Corporation Commission [Member]
Regulatory Proceedings [Line Items]
Return on equity, requested					9.85%
Rate-making equity ratio, requested					49.80%
Annual revenue increase (decrease) related to rebasing, requested					$ 6.7
One-time bill credit, requested		(36.9)
Annual revenue increase (decrease), requested, not including rebasing					$ 26.2
Public Utilities, Requested Rate Increase (Decrease) Following Stipulation, Amount		$ (3.9)
Public Utilities, Requested Return on Equity Following Stipulation		9.30%
Public Utilities, Requested Rate-Making Equity Ratio Following Stipulation		49.09%
FERC Proceedings [Member] | Westar Energy Inc [Member] | Federal Energy Regulatory Commission [Member]
Regulatory Proceedings [Line Items]
Annual transmissions revenue estimated amount of increase (decrease) over prior year									2.3	$ 29.6
Public Utilities, Estimated Annual Transmission Revenue Increase (Decrease) Over Prior Year Amount, Before Tax Rate Change Reduction									25.5
Public Utilities, Estimated Annual Transmission Revenue (Increase) Decrease Over Prior Year Amount, Reduction Due To Tax Rate Change									$ 23.2
Subsequent Event [Member] | FERC 2019 TFR Proceeding [Member] | Westar Energy Inc [Member] | Federal Energy Regulatory Commission [Member]
Regulatory Proceedings [Line Items]
Annual transmissions revenue estimated amount of increase (decrease) over prior year	$ (11.2)

Regulatory Matters Asset (Detai

Regulatory Matters Asset (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Regulatory Assets	$ 2,061.8	$ 784.9
Regulatory Assets, Current	(303.9)	(99.5)
Regulatory Assets, Noncurrent	1,757.9	685.4
Pension and post-retirement costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	808.2	393.9
Amount not included in rate base	764.5
Loss on reacquired debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets	113.5	109.2
Debt fair value adjustment [Member]
Regulatory Assets [Line Items]
Regulatory Assets	134.5	0
Asset retirement obligations fair value adjustment [Member]
Regulatory Assets [Line Items]
Regulatory Assets	111.4	0
Depreciation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	58	60.6
Removal Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	102.4	30.8
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	171.9	42.7
Analog meter unvrecovered investment [Member]
Regulatory Assets [Line Items]
Regulatory Assets	35.6	31.5
Amount not included in rate base	$ 27.3
Regulatory Asset, Amortization Period	5 years
Treasury Yield Hedge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 23.7	24.8
Iatan No. 1 and Common facilities depreciation and carrying costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	7.4	0
Iatan No. 2 construction accounting costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 26.8	0
Regulatory Noncurrent Asset, End Date for Recovery	Dec. 31, 2059
Kansas property tax surcharge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 33.1	17.4
Regulatory Asset, Amortization Period	1 year
Disallowed plant costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 15	15.2
LaCygne environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	14.8	13.3
Deferred customer programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	19.9	8.1
Amount not included in rate base	4.7
Fuel recovery mechanisms [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 91.2	20.7
Regulatory Asset, Amortization Period	1 year
Solar Rebates [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 45.2	0
Regulatory Noncurrent Asset, End Date for Recovery	Dec. 31, 2020
Transmission Delivery Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 0.8	0
Regulatory Asset, Amortization Period	1 year
Wolf Creek outage [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 21.8	7
Pension and other post-retirement benefit non-service costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	13.6	0
Retired Generation Facility [Member]
Regulatory Assets [Line Items]
Regulatory Assets	159.9	0
Merger transition costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 47	0
Regulatory Noncurrent Asset, End Date for Recovery	Dec. 31, 2028
Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 6.1	9.7
Westar Energy Inc [Member]
Regulatory Assets [Line Items]
Regulatory Assets	797.5	784.9
Regulatory Assets, Current	(97.1)	(99.5)
Regulatory Assets, Noncurrent	700.4	685.4
Westar Energy Inc [Member] | Pension and post-retirement costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	343.7	393.9
Amount not included in rate base	343.7
Westar Energy Inc [Member] | Loss on reacquired debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets	104.1	109.2
Westar Energy Inc [Member] | Debt fair value adjustment [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
Westar Energy Inc [Member] | Asset retirement obligations fair value adjustment [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
Westar Energy Inc [Member] | Depreciation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	58	60.6
Westar Energy Inc [Member] | Removal Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	65.7	30.8
Westar Energy Inc [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	49.5	42.7
Westar Energy Inc [Member] | Analog meter unvrecovered investment [Member]
Regulatory Assets [Line Items]
Regulatory Assets	35.6	31.5
Amount not included in rate base	$ 27.3
Regulatory Asset, Amortization Period	5 years
Westar Energy Inc [Member] | Treasury Yield Hedge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 23.7	24.8
Westar Energy Inc [Member] | Iatan No. 1 and Common facilities depreciation and carrying costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
Westar Energy Inc [Member] | Iatan No. 2 construction accounting costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
Westar Energy Inc [Member] | Kansas property tax surcharge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 23.7	17.4
Regulatory Asset, Amortization Period	1 year
Westar Energy Inc [Member] | Disallowed plant costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 15	15.2
Westar Energy Inc [Member] | LaCygne environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	12.2	13.3
Westar Energy Inc [Member] | Deferred customer programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	7	8.1
Westar Energy Inc [Member] | Fuel recovery mechanisms [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 7.1	20.7
Regulatory Asset, Amortization Period	1 year
Westar Energy Inc [Member] | Solar Rebates [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 0	0
Westar Energy Inc [Member] | Transmission Delivery Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
Westar Energy Inc [Member] | Wolf Creek outage [Member]
Regulatory Assets [Line Items]
Regulatory Assets	10.9	7
Westar Energy Inc [Member] | Pension and other post-retirement benefit non-service costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	5.2	0
Westar Energy Inc [Member] | Retired Generation Facility [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
Westar Energy Inc [Member] | Merger transition costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 22.6	0
Regulatory Noncurrent Asset, End Date for Recovery	Dec. 31, 2028
Westar Energy Inc [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 13.5	9.7
Westar Energy Inc [Member] | La Cygne Station [Member]
Regulatory Assets [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	50.00%
KCPL [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 626.1	698.7
Regulatory Assets, Current	(130.9)	(153.6)
Regulatory Assets, Noncurrent	495.2	545.1
KCPL [Member] | Pension and post-retirement costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	361.5	379.7
Amount not included in rate base	353.6
KCPL [Member] | Loss on reacquired debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets	8.2	8.7
KCPL [Member] | Debt fair value adjustment [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
KCPL [Member] | Asset retirement obligations fair value adjustment [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
KCPL [Member] | Depreciation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
KCPL [Member] | Removal Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	36.7	30.3
KCPL [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	91.6	94.3
KCPL [Member] | Analog meter unvrecovered investment [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
KCPL [Member] | Treasury Yield Hedge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
KCPL [Member] | Iatan No. 1 and Common facilities depreciation and carrying costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	2.9	12.9
KCPL [Member] | Iatan No. 2 construction accounting costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 13.5	25
Regulatory Noncurrent Asset, End Date for Recovery	Dec. 31, 2059
KCPL [Member] | Kansas property tax surcharge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 9.4	6.6
Regulatory Asset, Amortization Period	1 year
KCPL [Member] | Disallowed plant costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 0	0
KCPL [Member] | LaCygne environmental costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	2.6	2.7
KCPL [Member] | Deferred customer programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	8	40.9
Amount not included in rate base	4.7
KCPL [Member] | Fuel recovery mechanisms [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 41.7	61.7
Regulatory Asset, Amortization Period	1 year
KCPL [Member] | Solar Rebates [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 13.9	22.6
Regulatory Noncurrent Asset, End Date for Recovery	Dec. 31, 2020
KCPL [Member] | Transmission Delivery Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 0.8	3.2
Regulatory Asset, Amortization Period	1 year
KCPL [Member] | Wolf Creek outage [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 10.9	6.8
KCPL [Member] | Pension and other post-retirement benefit non-service costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	4.8	0
KCPL [Member] | Retired Generation Facility [Member]
Regulatory Assets [Line Items]
Regulatory Assets	0	0
KCPL [Member] | Merger transition costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 17.3	0
Regulatory Noncurrent Asset, End Date for Recovery	Dec. 31, 2028
KCPL [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets	$ 2.3	$ 3.3

Regulatory Matters Liabilities

Regulatory Matters Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 2,329	$ 1,105.6
Regulatory Liability, Current	(110.2)	(11.6)
Regulatory Liabilities, Noncurrent	2,218.8	1,094
Taxes refundable through future rates [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,703.6	845.2
Deferred regulatory gain from sale leaseback [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	59.1	64.6
Emission allowances [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	54.1	0
Nuclear decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	188.2	55.5
Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	53.4	48.4
Jurisdictional allowance for funds used during construction [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	30.3	31.7
La Cygne leasehold dismantling costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	29.5	29.6
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	48.1	0
Kansas tax credits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	16.5	16.8
Purchase power agreement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 8.8	8.8
Regulatory Liability, Amortization Period	5 years
Merger customer credits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 7.5	0
Refund of tax reform benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	70.9	0
Other Regulatory Assets (Liabilities) [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	59	5
Westar Energy Inc [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,121.3	1,105.6
Regulatory Liability, Current	(19.5)	(11.6)
Regulatory Liabilities, Noncurrent	1,101.8	1,094
Westar Energy Inc [Member] | Taxes refundable through future rates [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	853.2	845.2
Westar Energy Inc [Member] | Deferred regulatory gain from sale leaseback [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	59.1	64.6
Westar Energy Inc [Member] | Emission allowances [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Westar Energy Inc [Member] | Nuclear decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	84.5	55.5
Westar Energy Inc [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	28.3	48.4
Westar Energy Inc [Member] | Jurisdictional allowance for funds used during construction [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	30.3	31.7
Westar Energy Inc [Member] | La Cygne leasehold dismantling costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	29.5	29.6
Westar Energy Inc [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Westar Energy Inc [Member] | Kansas tax credits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	16.5	16.8
Westar Energy Inc [Member] | Purchase power agreement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 8.8	8.8
Regulatory Liability, Amortization Period	1 year
Westar Energy Inc [Member] | Merger customer credits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 0	0
Westar Energy Inc [Member] | Refund of tax reform benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	7.2	0
Westar Energy Inc [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	3.9	5
KCPL [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	847.1	779.2
Regulatory Liability, Current	(52.8)	(8.3)
Regulatory Liabilities, Noncurrent	794.3	770.9
KCPL [Member] | Taxes refundable through future rates [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	609.2	574
KCPL [Member] | Deferred regulatory gain from sale leaseback [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
KCPL [Member] | Emission allowances [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	54.1	58.1
KCPL [Member] | Nuclear decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	103.7	126
KCPL [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	25.1	12
KCPL [Member] | Jurisdictional allowance for funds used during construction [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
KCPL [Member] | La Cygne leasehold dismantling costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
KCPL [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
KCPL [Member] | Kansas tax credits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
KCPL [Member] | Purchase power agreement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
KCPL [Member] | Merger customer credits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	7.5	0
KCPL [Member] | Refund of tax reform benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	36.3	0
KCPL [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 11.2	$ 9.1

Rate Matters and Regulation Reg

Rate Matters and Regulation Regulatory Matters Subsequent Events (Details) - Westar Energy Inc [Member] - Federal Energy Regulatory Commission [Member] - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
FERC Proceedings [Member]
Subsequent Event [Line Items]
Annual transmissions revenue estimated amount of increase (decrease) over prior year		$ 2.3	$ 29.6
FERC 2019 TFR Proceeding [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Annual transmissions revenue estimated amount of increase (decrease) over prior year	$ (11.2)

Asset Retirement Obligations (D

Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 405.1	$ 324
Liabilities assumed upon merger with Great Plains Energy	412.2	0
Liabilities incurred during the year	7.4	13.5
Revision in timing and/or estimates	(150.1)	66.8
Settlements	(22.4)	(16)
Accretion	34.9	16.8
Ending balance	687.1	405.1
Less: current portion	(49.8)	(25.1)
Total noncurrent asset retirement obligation	637.3	380
Wolf Creek [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Revision in timing and/or estimates	(127)
Jointly owned utility plant, proportionate ownership share			94.00%	94.00%
Westar Energy Inc [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	405.1	324
Liabilities assumed upon merger with Great Plains Energy	0	0
Liabilities incurred during the year	7.4	13.5
Revision in timing and/or estimates	(138.7)	66.8
Settlements	(12)	(16)
Accretion	19.3	16.8
Ending balance	281.1	405.1
Less: current portion	(17.1)	(25.1)
Total noncurrent asset retirement obligation	264	380
Westar Energy Inc [Member] | Wolf Creek [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Revision in timing and/or estimates	(127)
Jointly owned utility plant, proportionate ownership share			47.00%	47.00%
KCPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	266.3	278
Liabilities assumed upon merger with Great Plains Energy	0	0
Liabilities incurred during the year	0	0
Revision in timing and/or estimates	(11.4)	0.3
Settlements	(13.1)	(25.5)
Accretion	19.2	13.5
Ending balance	261	266.3
Less: current portion	(29.2)	(34.9)
Total noncurrent asset retirement obligation	$ 231.8	$ 231.4
KCPL [Member] | Wolf Creek [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Jointly owned utility plant, proportionate ownership share			47.00%	47.00%

Property, Plant & Equipment P_3

Property, Plant & Equipment Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation	$ 567.9	$ 350	$ 316.7
Electric plant in service	26,916.7	12,954.3
Electric plant acquisition adjustment	740.6	739
Accumulated depreciation	(9,694.1)	(4,651.7)
Plant in service	17,963.2	9,041.6
Construction work in progress	685.2	434.9
Nuclear fuel, net	133.1	71.4
Plant To Be Retired, Net	1	5.9
Property, plant and equipment, net	18,782.5	9,553.8
Variable Interest Entities [Member]
Property, Plant and Equipment [Line Items]
Depreciation	7.1	8.3	9.5
Electric plant in service	392.1	392.1
Accumulated depreciation	(222.9)	(215.8)
Property, plant and equipment, net	169.2	176.3
Westar Energy Inc [Member]
Property, Plant and Equipment [Line Items]
Depreciation	371.3	350	316.7
Electric plant in service	13,176.7	12,954.3
Electric plant acquisition adjustment	740.6	739
Accumulated depreciation	(4,642.8)	(4,651.7)
Plant in service	9,274.5	9,041.6
Construction work in progress	376.7	434.9
Nuclear fuel, net	66.1	71.4
Plant To Be Retired, Net	1	5.9
Property, plant and equipment, net	9,718.3	9,553.8
Westar Energy Inc [Member] | Variable Interest Entities [Member]
Property, Plant and Equipment [Line Items]
Depreciation	7.1	8.3	9.5
Electric plant in service	392.1	392.1
Accumulated depreciation	(222.9)	(215.8)
Property, plant and equipment, net	169.2	176.3
KCPL [Member]
Property, Plant and Equipment [Line Items]
Depreciation	235.3	228.4	$ 215.4
Electric plant in service	10,439.1	10,213.2
Electric plant acquisition adjustment	0	0
Accumulated depreciation	(4,022.4)	(4,070.3)
Plant in service	6,416.7	6,142.9
Construction work in progress	204.4	350.3
Nuclear fuel, net	67	72.4
Plant To Be Retired, Net	0	0
Property, plant and equipment, net	$ 6,688.1	$ 6,565.6

Jointly Owned Electric Utilit_3

Jointly Owned Electric Utility Plants (Details) $ in Millions	Dec. 31, 2018USD ($)	Dec. 31, 2018Rate	Dec. 31, 2018MW	Dec. 31, 2018	Dec. 31, 2017USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Nuclear fuel, net	$ 133.1				$ 71.4
Iatan Common [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		79.00%
Utility plant in service	504.9
Accumulated depreciation	127.8
Nuclear fuel, net	0
Construction work in progress	26.5
Jeffrey Energy Center [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		100.00%
Utility plant in service	2,392.5
Accumulated depreciation	861
Nuclear fuel, net	0
Construction work in progress	33.2
Accredited capacity | MW			2,187
Leasehold Interest Percentage | Rate		8.00%
Iatan No. 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		73.00%
Utility plant in service	1,374.5
Accumulated depreciation	426.7
Nuclear fuel, net	0
Construction work in progress	30.5
Accredited capacity | MW			641
Iatan No. 1 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		88.00%
Utility plant in service	707.3
Accumulated depreciation	257.3
Nuclear fuel, net	0
Construction work in progress	27.1
Accredited capacity | MW			616
LaCygne Station [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		100.00%
Utility plant in service	2,228
Accumulated depreciation	737.1
Nuclear fuel, net	0
Construction work in progress	41.8
Accredited capacity | MW			1,398
Wolf Creek [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share		94.00%		94.00%
Utility plant in service	3,724.9
Accumulated depreciation	1,760.8
Nuclear fuel, net	133.1
Construction work in progress	171.6
Accredited capacity | MW			1,104
State Line [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		40.00%
Utility plant in service	114.1
Accumulated depreciation	71.3
Nuclear fuel, net	0
Construction work in progress	0.4
Accredited capacity | MW			196
La Cygne Unit 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Leasehold Interest Percentage | Rate		50.00%
KCPL [Member]
Jointly Owned Utility Plant Interests [Line Items]
Nuclear fuel, net	67				72.4
KCPL [Member] | Iatan Common [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		61.00%
Utility plant in service	414.8
Accumulated depreciation	112.8
Nuclear fuel, net	0
Construction work in progress	15
KCPL [Member] | Iatan No. 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		55.00%
Utility plant in service	1,060.3
Accumulated depreciation	378.4
Nuclear fuel, net	0
Construction work in progress	6.2
Accredited capacity | MW			482
KCPL [Member] | Iatan No. 1 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		70.00%
Utility plant in service	567.4
Accumulated depreciation	203.2
Nuclear fuel, net	0
Construction work in progress	3.3
Accredited capacity | MW			490
KCPL [Member] | LaCygne Station [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		50.00%
Utility plant in service	1,194.5
Accumulated depreciation	328.5
Nuclear fuel, net	0
Construction work in progress	7.8
Accredited capacity | MW			699
KCPL [Member] | Wolf Creek [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share		47.00%		47.00%
Utility plant in service	1,891.2
Accumulated depreciation	935.5
Nuclear fuel, net	67
Construction work in progress	87.9
Accredited capacity | MW			552
Westar Energy Inc [Member]
Jointly Owned Utility Plant Interests [Line Items]
Nuclear fuel, net	66.1				$ 71.4
Westar Energy Inc [Member] | Jeffrey Energy Center [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		92.00%
Utility plant in service	2,189.6
Accumulated depreciation	778.6
Nuclear fuel, net	0
Construction work in progress	30.6
Accredited capacity | MW			2,012
Leasehold Interest Percentage | Rate		8.00%
Westar Energy Inc [Member] | LaCygne Station [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		50.00%
Utility plant in service	1,033.5
Accumulated depreciation	408.6
Nuclear fuel, net	0
Construction work in progress	34
Accredited capacity | MW			699
Westar Energy Inc [Member] | Wolf Creek [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share		47.00%		47.00%
Utility plant in service	1,833.7
Accumulated depreciation	825.3
Nuclear fuel, net	66.1
Construction work in progress	83.7
Accredited capacity | MW			552
Westar Energy Inc [Member] | State Line [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share | Rate		40.00%
Utility plant in service	114.1
Accumulated depreciation	71.3
Nuclear fuel, net	0
Construction work in progress	$ 0.4
Accredited capacity | MW			196
Westar Energy Inc [Member] | La Cygne Unit 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Leasehold Interest Percentage | Rate		50.00%

Pension Plans and Other Emplo_3

Pension Plans and Other Employee Benefits Pension Plans Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount		$ 607.6
Fair Value of Plan Assets	$ 1,603.4	887	$ 797.2
Actual return on plan assets [Abstract]
Fair Value, Assets, Level 2 To Alternative Investments Transfers, Amount		160.4
Pension Plan [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	798.8	848.4	776.8
Pension Plan [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	804.6	887	797.2
Pension Plan [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	238.1	263.9
Pension Plan [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	215	256.1
Pension Plan [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	150.9	176
Pension Plan [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	138.7	177.9
Pension Plan [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	123.6	125.8
Pension Plan [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	69.9	69.8
Pension Plan [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5.5	5.9
Pension Plan [Member] | Real estate investments [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	48.2	46.4
Pension Plan [Member] | Real estate investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	44.8	41.8
Pension Plan [Member] | Combination debt/equity/other fund [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	13.5	15.9
Pension Plan [Member] | Combination debt/equity/other fund [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	30.1	36.2
Pension Plan [Member] | Alternative investment funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	31.6	32.7
Pension Plan [Member] | Alternative investment funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	73.6	70.3
Pension Plan [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	6	5.2
Pension Plan [Member] | Other [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.3	4.6
Pension Plan [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	49.8	35.6
Pension Plan [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	67.4	71.8
Pension Plan [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	296.4	299.5
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	450.2	482
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	522	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	198.6	220.5
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	144.7	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	104	123.5
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	91.8	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	52.4	51.5
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Real estate investments [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	12.6	13.6
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Real estate investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Combination debt/equity/other fund [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	13.5	15.9
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Combination debt/equity/other fund [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	30.1	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Alternative investment funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Alternative investment funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Other [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	49.8	35.6
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	19.3	21.4
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	255.4	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	146.9	154.6
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	768
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	232.2
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	177.9
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	123.6	125.8
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	17.5	18.3
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5.5	5.9
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Real estate investments [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Real estate investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Combination debt/equity/other fund [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Combination debt/equity/other fund [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	36.2
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Alternative investment funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Alternative investment funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	17
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	5.2
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Other [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.3	4.6
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	299.5
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Real estate investments [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Real estate investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Combination debt/equity/other fund [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Combination debt/equity/other fund [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Alternative investment funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Alternative investment funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Other [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	201.7	211.8
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	282.6	119
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	39.5	43.4
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	70.3	23.9
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	46.9	52.5
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	46.9	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Real estate investments [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	35.6	32.8
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Real estate investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	44.8	41.8
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Combination debt/equity/other fund [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Combination debt/equity/other fund [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Alternative investment funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	31.6	32.7
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Alternative investment funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	73.6	53.3
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	6	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Other [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	48.1	50.4
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	41	0
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	223.3	124.1	115.6
Actual return on plan assets [Abstract]
Fair Value, Assets, Level 2 To Alternative Investments Transfers, Amount		124.1
Other Postretirement Benefits Plan [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	113.6	115.8	115.6
Contributions by employer, remainder of fiscal year	4.6
Other Postretirement Benefits Plan [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	109.7	124.1	$ 115.6
Other Postretirement Benefits Plan [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2.5	3.7
Other Postretirement Benefits Plan [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	56.4	65.2
Other Postretirement Benefits Plan [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.9
Other Postretirement Benefits Plan [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	14	16.2
Other Postretirement Benefits Plan [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	17.4	16.7
Other Postretirement Benefits Plan [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	10.3	8.5
Other Postretirement Benefits Plan [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2.5	3.6
Other Postretirement Benefits Plan [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.7
Other Postretirement Benefits Plan [Member] | Other [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.3	1.4
Other Postretirement Benefits Plan [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	4.7	25.3
Other Postretirement Benefits Plan [Member] | Cash and Cash Equivalents [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.2	0.6
Other Postretirement Benefits Plan [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	75	56.6
Other Postretirement Benefits Plan [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	38.4	42.1
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	10.9	32.2
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.2	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2.5	3.7
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.9
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2.6	3
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	4.7	25.3
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.2	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.2	0.2
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	27.9	27.2
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	124.1
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	65.2
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	16.2
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	17.4	16.7
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	7.7	5.5
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2.5	3.6
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Other [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.3	1.4
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0.6
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	42.1
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Other [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	74.8	56.4
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	109.5	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Domestic equities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	56.4	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | International equity [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | International equity [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	14	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Corporate bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | US Treasury and agency bonds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Short-term investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.7
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Other [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Cash and Cash Equivalents [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Bond funds [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	74.8	56.4
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Bond funds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 38.4	$ 0

Pension Plans and Other Emplo_4

Pension Plans and Other Employee Benefits Pension Plans and Post-Retirement Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2018
Employee Savings Plans
Defined Contribution Plan, Cost	$ 16.3	$ 9.7	$ 9.6
Westar Energy Inc [Member]
Employee Savings Plans
Defined Contribution Plan, Cost	9.9	9.7	9.6
KCPL [Member]
Employee Savings Plans
Defined Contribution Plan, Cost	8.3	7.7	8
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, beginning of the year	1,367	1,241
Service cost	60.7	28.7	25.3
Interest cost	82.5	52.4	53.4
Contributions by participants	0	0
Plan amendments	13.4
Actuarial (gain) loss	(98.8)	107
Benefits paid	(137.9)	(62.1)
Settlements and special termination benefits		0
Obligations assumed upon merger with Great Plains Energy	1,275.9
Other	(9.4)
Defined Benefit Plan, Benefit Obligation, end of the year	2,553.4	1,367	1,241
Change in plan assets
Fair value of plan assets, beginning of the year	887	797.2
Actual return on plan assets	(79.7)	113.1
Contributions by employer and participants	114.5	36.3
Benefits paid	(134)	(59.6)
Settlements		0
Assets acquired upon merger with Great Plains Energy	825
Other	(9.4)
Fair value of plan assets, end of the year	1,603.4	887	797.2
Funded status at end of year	(950)	(480)
Amounts recognized in the consolidated balance sheets
Non-current asset	0	0
Current pension and other post-retirement liability	(4.4)	(2.5)
Noncurrent pension liability and other post-retirement liability	(945.6)	(477.5)
Net amount recognized before regulatory treatment	(950)	(480)
Accumulated OCI or regulatory asset/liability	419.9	372.6
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(530.1)	(107.4)
Amounts in accumulated other comprehensive income or regulatory asset/liability not yet recognized as a component of net periodic benefit cost [Abstract]
Actuarial (gain) loss	403.6	369
Prior service cost	16.3	3.6
Other	0	0
Accumulated OCI or regulatory asset/liability	419.9	372.6
Unfunded accumulated benefit obligation for non qualified plans	46.9	27.4
Segregated assets for non-qualified benefit plans	43.8	34.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	60.7	28.7	25.3
Interest cost	82.5	52.4	53.4
Expected return on plan assets	(86.4)	(53.6)	(52.3)
Prior service cost	0.7	0.7	0.8
Settlement and special termination benefits		0.4
Recognized net actuarial (gain) loss	32.6	26.9	24.9
Net periodic benefit costs before regulatory adjustment and intercompany allocations	90.1	55.5	52.1
Regulatory adjustment	8.3	14.5	16.4
Net periodic benefit costs	98.4	70	68.5
Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income Regulatory Assets/Liabilities [Abstract]
Current year net (gain) loss	67.2	47.1	62.8
Amortization of gain (loss)	(32.6)	(26.9)	(24.9)
Prior service cost	13.4		(3.4)
Amortization of prior service cost	(0.7)	(0.7)	(0.8)
Other regulatory activity	0	0	0
Total Recognized In OCI Or Regulatory Asset Liability	47.3	19.5	33.7
Total Recognized In Net Periodic Benefit Costs And OCI Or Regulatory Asset Liability	145.7	89.5	102.2
Prior service cost amortization	1.9
Actuarial gain (loss) amortization	27.5
ABO for all defined benefit pension plans	2,257.9	1,219.6
Pension plans with the PBO in excess of plan assets
Projected benefit obligation	2,553.4	1,367
Fair value of plan assets	1,603.4	887
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	2,257.9	1,219.6
Fair value of plan assets	$ 1,603.4	$ 887
Weighted-average assumptions used to determine the benefit obligation
Discount rate		3.73%			4.35%
Rate of compensation increase		4.00%			3.76%
Weighted-average assumptions used to determine net costs
Discount rate	3.73%	4.25%
Expected long-term return on plan assets	6.52%	6.64%
Rate of compensation increase	3.92%	4.00%
Contributions to plans in next year	$ 115.5
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	193
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	188.9
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	189.4
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	187.4
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	186.1
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	928.7
Pension Plan [Member] | Westar Energy Inc [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, beginning of the year	1,367	$ 1,241
Service cost	32.2	28.7	25.3
Interest cost	50.7	52.4	53.4
Contributions by participants	0	0
Plan amendments	11.4
Actuarial (gain) loss	(100.1)	107
Benefits paid	(97.9)	(62.1)
Settlements and special termination benefits		0
Obligations assumed upon merger with Great Plains Energy	0
Other	(4.4)
Defined Benefit Plan, Benefit Obligation, end of the year	1,258.9	1,367	1,241
Change in plan assets
Fair value of plan assets, beginning of the year	887	797.2
Actual return on plan assets	(30.9)	113.1
Contributions by employer and participants	47.9	36.3
Benefits paid	(95)	(59.6)
Settlements		0
Assets acquired upon merger with Great Plains Energy	0
Other	(4.4)
Fair value of plan assets, end of the year	804.6	887	797.2
Funded status at end of year	(454.3)	(480)
Amounts recognized in the consolidated balance sheets
Non-current asset	0	0
Current pension and other post-retirement liability	(2.6)	(2.5)
Noncurrent pension liability and other post-retirement liability	(451.7)	(477.5)
Net amount recognized before regulatory treatment	(454.3)	(480)
Accumulated OCI or regulatory asset/liability	337.5	372.6
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(116.8)	(107.4)
Amounts in accumulated other comprehensive income or regulatory asset/liability not yet recognized as a component of net periodic benefit cost [Abstract]
Actuarial (gain) loss	323.2	369
Prior service cost	14.3	3.6
Other	0	0
Accumulated OCI or regulatory asset/liability	337.5	372.6
Unfunded accumulated benefit obligation for non qualified plans	24.8	27.4
Segregated assets for non-qualified benefit plans	30.6	34.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	32.2	28.7	25.3
Interest cost	50.7	52.4	53.4
Expected return on plan assets	(55.9)	(53.6)	(52.3)
Prior service cost	0.7	0.7	0.8
Settlement and special termination benefits		0.4
Recognized net actuarial (gain) loss	32.6	26.9	24.9
Net periodic benefit costs before regulatory adjustment and intercompany allocations	60.3	55.5	52.1
Regulatory adjustment	8.8	14.5	16.4
Intercompany allocations	0	0	0
Net periodic benefit costs	69.1	70	68.5
Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income Regulatory Assets/Liabilities [Abstract]
Current year net (gain) loss	(13.2)	47.1	62.8
Amortization of gain (loss)	(32.6)	(26.9)	(24.9)
Prior service cost	11.4		(3.4)
Amortization of prior service cost	(0.7)	(0.7)	(0.8)
Other regulatory activity	0	0	0
Total Recognized In OCI Or Regulatory Asset Liability	(35.1)	19.5	33.7
Total Recognized In Net Periodic Benefit Costs And OCI Or Regulatory Asset Liability	34	89.5	102.2
Prior service cost amortization	1.7
Actuarial gain (loss) amortization	25.4
ABO for all defined benefit pension plans	1,139.1	1,219.6
Pension plans with the PBO in excess of plan assets
Projected benefit obligation	1,258.9	1,367
Fair value of plan assets	804.6	887
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	1,139.1	1,219.6
Fair value of plan assets	$ 804.6	$ 887
Weighted-average assumptions used to determine the benefit obligation
Discount rate		3.73%			4.35%
Rate of compensation increase		4.00%			4.03%
Weighted-average assumptions used to determine net costs
Discount rate	3.73%	4.25%
Expected long-term return on plan assets	6.67%	6.64%
Rate of compensation increase	4.00%	4.00%
Contributions to plans in next year	$ 37
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	96.7
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	94.9
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	95.3
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	92.7
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	90
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	432.7
Pension Plan [Member] | KCPL [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, beginning of the year	1,331.7	$ 1,220.6
Service cost	48.6	44.2	42
Interest cost	49.9	52.6	52.9
Contributions by participants	0	0
Plan amendments	2
Actuarial (gain) loss	(89.6)	134.9
Benefits paid	(70.2)	(34.7)
Settlements and special termination benefits		(85.9)
Obligations assumed upon merger with Great Plains Energy	0
Other	0
Defined Benefit Plan, Benefit Obligation, end of the year	1,272.4	1,331.7	1,220.6
Change in plan assets
Fair value of plan assets, beginning of the year	848.4	776.8
Actual return on plan assets	(60.1)	114.8
Contributions by employer and participants	80.3	76.9
Benefits paid	(69.8)	(34.5)
Settlements		(85.6)
Assets acquired upon merger with Great Plains Energy	0
Other	0
Fair value of plan assets, end of the year	798.8	848.4	776.8
Funded status at end of year	(473.6)	(483.3)
Amounts recognized in the consolidated balance sheets
Non-current asset	0	0
Current pension and other post-retirement liability	(0.5)	(0.6)
Noncurrent pension liability and other post-retirement liability	(473.1)	(482.7)
Net amount recognized before regulatory treatment	(473.6)	(483.3)
Accumulated OCI or regulatory asset/liability	362.4	379.7
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(111.2)	(103.6)
Amounts in accumulated other comprehensive income or regulatory asset/liability not yet recognized as a component of net periodic benefit cost [Abstract]
Actuarial (gain) loss	226.3	245.5
Prior service cost	3.8	2.5
Other	132.3	131.7
Accumulated OCI or regulatory asset/liability	362.4	379.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	48.6	44.2	42
Interest cost	49.9	52.6	52.9
Expected return on plan assets	(55.5)	(51.2)	(49.2)
Prior service cost	0.7	0.7	0.7
Settlement and special termination benefits		16.3
Recognized net actuarial (gain) loss	45.1	49	51.8
Net periodic benefit costs before regulatory adjustment and intercompany allocations	88.8	111.6	98.2
Regulatory adjustment	0.7	(9.2)	(3.1)
Intercompany allocations	(21.6)	(37.1)	(36)
Net periodic benefit costs	67.9	65.3	59.1
Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income Regulatory Assets/Liabilities [Abstract]
Current year net (gain) loss	25.9	71.3	63.6
Amortization of gain (loss)	(45.1)	(64.9)	(51.8)
Prior service cost	2		0
Amortization of prior service cost	(0.7)	(0.7)	(0.7)
Other regulatory activity	0.6	6.1	(2.9)
Total Recognized In OCI Or Regulatory Asset Liability	(17.3)	11.8	8.2
Total Recognized In Net Periodic Benefit Costs And OCI Or Regulatory Asset Liability	50.6	77.1	67.3
Prior service cost amortization	0.9
Actuarial gain (loss) amortization	48.3
ABO for all defined benefit pension plans	1,096.7	1,155.5
Pension plans with the PBO in excess of plan assets
Projected benefit obligation	1,272.4	1,331.7
Fair value of plan assets	798.8	848.4
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	1,096.7	1,155.5
Fair value of plan assets	$ 798.8	$ 848.4
Weighted-average assumptions used to determine the benefit obligation
Discount rate		3.72%			4.36%
Rate of compensation increase		3.62%			3.64%
Weighted-average assumptions used to determine net costs
Discount rate	3.72%	4.31%
Expected long-term return on plan assets	6.46%	6.73%
Rate of compensation increase	3.62%	3.62%
Contributions to plans in next year	$ 78.5
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	94.9
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	92.8
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	92.8
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	93.4
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	94.7
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	488.3
Pension Plan [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	256.1
Fair value of plan assets, end of the year	215	$ 256.1
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					29.00%
Pension Plan [Member] | Domestic equities [Member] | KCPL [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	263.9
Fair value of plan assets, end of the year	238.1	263.9
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					32.00%
Pension Plan [Member] | International equity [Member] | Westar Energy Inc [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	177.9
Fair value of plan assets, end of the year	138.7	177.9
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					20.00%
Pension Plan [Member] | International equity [Member] | KCPL [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	176
Fair value of plan assets, end of the year	150.9	176
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					21.00%
Pension Plan [Member] | Bonds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					36.00%
Pension Plan [Member] | Bonds [Member] | KCPL [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					36.00%
Pension Plan [Member] | Mortgage & asset-backed securities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					0.00%
Pension Plan [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	5.9
Fair value of plan assets, end of the year	5.5	5.9
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					0.00%
Pension Plan [Member] | Real estate investments [Member] | Westar Energy Inc [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	41.8
Fair value of plan assets, end of the year	44.8	41.8
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					4.00%
Pension Plan [Member] | Real estate investments [Member] | KCPL [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	46.4
Fair value of plan assets, end of the year	48.2	46.4
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					6.00%
Pension Plan [Member] | Other investments | Westar Energy Inc [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					11.00%
Pension Plan [Member] | Other investments | KCPL [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					5.00%
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, beginning of the year	138.6	136.8
Service cost	2.3	1.2	1.2
Interest cost	8	5.5	5.9
Contributions by participants	5.6	1.5
Plan amendments	0
Actuarial (gain) loss	(11.3)	2.8
Benefits paid	(17.3)	(9.2)
Settlements and special termination benefits		0
Obligations assumed upon merger with Great Plains Energy	123.4
Other	0
Defined Benefit Plan, Benefit Obligation, end of the year	249.3	138.6	136.8
Change in plan assets
Fair value of plan assets, beginning of the year	124.1	115.6
Actual return on plan assets	(7.5)	15.6
Contributions by employer and participants	11.6	1.9
Benefits paid	(16.7)	(9)
Settlements		0
Assets acquired upon merger with Great Plains Energy	111.8
Other	0
Fair value of plan assets, end of the year	223.3	124.1	115.6
Funded status at end of year	(26)	(14.5)
Amounts recognized in the consolidated balance sheets
Non-current asset	17.5	0
Current pension and other post-retirement liability	(1.7)	(0.8)
Noncurrent pension liability and other post-retirement liability	(41.8)	(13.7)
Net amount recognized before regulatory treatment	(26)	(14.5)
Accumulated OCI or regulatory asset/liability	(6)	(11.1)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(32)	(25.6)
Amounts in accumulated other comprehensive income or regulatory asset/liability not yet recognized as a component of net periodic benefit cost [Abstract]
Actuarial (gain) loss	(7.8)	(13.3)
Prior service cost	1.8	2.2
Other	0	0
Accumulated OCI or regulatory asset/liability	(6)	(11.1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2.3	1.2	1.2
Interest cost	8	5.5	5.9
Expected return on plan assets	(8.8)	(6.9)	(6.9)
Prior service cost	0.5	0.5	0.5
Settlement and special termination benefits		0
Recognized net actuarial (gain) loss	(0.6)	(0.8)	(1.1)
Net periodic benefit costs before regulatory adjustment and intercompany allocations	1.4	(0.5)	(0.4)
Regulatory adjustment	(1.7)	(1.9)	(1.9)
Net periodic benefit costs	(0.3)	(2.4)	(2.3)
Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income Regulatory Assets/Liabilities [Abstract]
Current year net (gain) loss	4.9	(5.8)	3.1
Amortization of gain (loss)	0.6	0.8	1.1
Prior service cost	0		0
Amortization of prior service cost	(0.5)	(0.5)	(0.5)
Other regulatory activity	0	0	0
Total Recognized In OCI Or Regulatory Asset Liability	5	(5.5)	3.7
Total Recognized In Net Periodic Benefit Costs And OCI Or Regulatory Asset Liability	4.7	(7.9)	1.4
Prior service cost amortization	0.5
Actuarial gain (loss) amortization	(1.2)
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	249.3	138.6
Fair value of plan assets	$ 223.3	$ 124.1
Weighted-average assumptions used to determine the benefit obligation
Discount rate		3.67%			4.33%
Rate of compensation increase		4.00%			3.50%
Weighted-average assumptions used to determine net costs
Discount rate	3.67%	4.31%
Expected long-term return on plan assets	6.00%	6.00%
Rate of compensation increase	3.50%	4.00%
Contributions to plans in next year	$ 2.8
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	20.3
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	19.8
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	20.6
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	21.1
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	21.5
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	$ 110.7
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Health care cost trend rate assumed for next year		6.00%			6.50%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)		5.00%			4.50%
Year that rate reaches ultimate trend	2,027	2,020
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	$ 0
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	0.2
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components	0
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	(0.1)
Other Postretirement Benefits Plan [Member] | Westar Energy Inc [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, beginning of the year	138.6	$ 136.8
Service cost	1.3	1.2	1.2
Interest cost	5	5.5	5.9
Contributions by participants	1.8	1.5
Plan amendments	0
Actuarial (gain) loss	(2.6)	2.8
Benefits paid	(10.5)	(9.2)
Settlements and special termination benefits		0
Obligations assumed upon merger with Great Plains Energy	0
Other	0
Defined Benefit Plan, Benefit Obligation, end of the year	133.6	138.6	136.8
Change in plan assets
Fair value of plan assets, beginning of the year	124.1	115.6
Actual return on plan assets	(7.4)	15.6
Contributions by employer and participants	3.2	1.9
Benefits paid	(10.2)	(9)
Settlements		0
Assets acquired upon merger with Great Plains Energy	0
Other	0
Fair value of plan assets, end of the year	109.7	124.1	115.6
Funded status at end of year	(23.9)	(14.5)
Amounts recognized in the consolidated balance sheets
Non-current asset	0	0
Current pension and other post-retirement liability	(0.9)	(0.8)
Noncurrent pension liability and other post-retirement liability	(23)	(13.7)
Net amount recognized before regulatory treatment	(23.9)	(14.5)
Accumulated OCI or regulatory asset/liability	0.8	(11.1)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(23.1)	(25.6)
Amounts in accumulated other comprehensive income or regulatory asset/liability not yet recognized as a component of net periodic benefit cost [Abstract]
Actuarial (gain) loss	(1)	(13.3)
Prior service cost	1.8	2.2
Other	0	0
Accumulated OCI or regulatory asset/liability	0.8	(11.1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1.3	1.2	1.2
Interest cost	5	5.5	5.9
Expected return on plan assets	(7)	(6.9)	(6.9)
Prior service cost	0.5	0.5	0.5
Settlement and special termination benefits		0
Recognized net actuarial (gain) loss	(0.6)	(0.8)	(1.1)
Net periodic benefit costs before regulatory adjustment and intercompany allocations	(0.8)	(0.5)	(0.4)
Regulatory adjustment	(2)	(1.9)	(1.9)
Intercompany allocations	0	0	0
Net periodic benefit costs	(2.8)	(2.4)	(2.3)
Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income Regulatory Assets/Liabilities [Abstract]
Current year net (gain) loss	11.7	(5.8)	3.1
Amortization of gain (loss)	0.6	0.8	1.1
Prior service cost	0		0
Amortization of prior service cost	(0.5)	(0.5)	(0.5)
Other regulatory activity	0	0	0
Total Recognized In OCI Or Regulatory Asset Liability	11.8	(5.5)	3.7
Total Recognized In Net Periodic Benefit Costs And OCI Or Regulatory Asset Liability	9	(7.9)	1.4
Prior service cost amortization	0.5
Actuarial gain (loss) amortization	(0.5)
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	133.6	138.6
Fair value of plan assets	$ 109.7	$ 124.1
Weighted-average assumptions used to determine the benefit obligation
Discount rate		3.67%			4.33%
Rate of compensation increase		4.00%
Weighted-average assumptions used to determine net costs
Discount rate	3.73%	4.31%
Expected long-term return on plan assets	6.00%	6.00%
Rate of compensation increase		4.00%
Contributions to plans in next year	$ 0.7
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	10.9
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	11
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	11.3
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	11.5
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	11.7
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	$ 58.5
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Health care cost trend rate assumed for next year		6.00%			6.50%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)		5.00%			4.50%
Year that rate reaches ultimate trend	2,027	2,020
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	$ 0
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	(0.1)
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components	0
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	(0.1)
Other Postretirement Benefits Plan [Member] | KCPL [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, beginning of the year	133.2	$ 130.1
Service cost	2	2.1	2.6
Interest cost	4.8	5.4	6.1
Contributions by participants	6.6	6
Plan amendments	0
Actuarial (gain) loss	(18)	2.1
Benefits paid	(12.9)	(12.5)
Settlements and special termination benefits		0
Obligations assumed upon merger with Great Plains Energy	0
Other	0
Defined Benefit Plan, Benefit Obligation, end of the year	115.7	133.2	130.1
Change in plan assets
Fair value of plan assets, beginning of the year	115.8	115.6
Actual return on plan assets	(1.2)	1.8
Contributions by employer and participants	11.4	10.4
Benefits paid	(12.4)	(12)
Settlements		0
Assets acquired upon merger with Great Plains Energy	0
Other	0
Fair value of plan assets, end of the year	113.6	115.8	115.6
Funded status at end of year	(2.1)	(17.4)
Amounts recognized in the consolidated balance sheets
Non-current asset	17.5	12.8
Current pension and other post-retirement liability	(0.8)	(0.8)
Noncurrent pension liability and other post-retirement liability	(18.8)	(29.4)
Net amount recognized before regulatory treatment	(2.1)	(17.4)
Accumulated OCI or regulatory asset/liability	(26)	(12.2)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(28.1)	(29.6)
Amounts in accumulated other comprehensive income or regulatory asset/liability not yet recognized as a component of net periodic benefit cost [Abstract]
Actuarial (gain) loss	(11)	2.8
Prior service cost	(8.1)	(8)
Other	(6.9)	(7)
Accumulated OCI or regulatory asset/liability	(26)	(12.2)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2.1	2.6
Interest cost	4.8	5.4	6.1
Expected return on plan assets	(2.8)	(2.5)	(3)
Prior service cost	0.1	0	1.2
Settlement and special termination benefits		0
Recognized net actuarial (gain) loss	(0.2)	(0.5)	(1.5)
Net periodic benefit costs before regulatory adjustment and intercompany allocations	3.9	4.5	5.4
Regulatory adjustment	(0.1)	1.3	3.6
Intercompany allocations	(1.1)	(1.5)	(1.9)
Net periodic benefit costs	2.7	4.3	7.1
Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income Regulatory Assets/Liabilities [Abstract]
Current year net (gain) loss	(14)	3	1
Amortization of gain (loss)	0.2	0.5	1.5
Prior service cost	0		(10.1)
Amortization of prior service cost	(0.1)	0	(1.2)
Other regulatory activity	0	0	(1.9)
Total Recognized In OCI Or Regulatory Asset Liability	(13.9)	3.5	(10.7)
Total Recognized In Net Periodic Benefit Costs And OCI Or Regulatory Asset Liability	(11.2)	7.8	$ (3.6)
Prior service cost amortization	0
Actuarial gain (loss) amortization	(1.5)
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	57.7	111.6
Fair value of plan assets	$ 38.2	$ 81.5
Weighted-average assumptions used to determine the benefit obligation
Discount rate		3.64%			4.33%
Rate of compensation increase		3.50%			3.50%
Weighted-average assumptions used to determine net costs
Discount rate	3.64%	4.20%
Expected long-term return on plan assets	2.80%	2.00%
Rate of compensation increase	3.50%	3.50%
Contributions to plans in next year	$ 2.1
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	9.4
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	8.9
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	9.3
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	9.6
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	9.8
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	$ 52.1
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Health care cost trend rate assumed for next year		6.80%			6.50%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)		4.50%			4.50%
Year that rate reaches ultimate trend	2,027	2,027
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	$ 0.1
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	0
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components	0.3
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	(0.2)
Other Postretirement Benefits Plan [Member] | Domestic equities [Member] | Westar Energy Inc [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	65.2
Fair value of plan assets, end of the year	56.4	$ 65.2
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					52.00%
Other Postretirement Benefits Plan [Member] | Domestic equities [Member] | KCPL [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	3.7
Fair value of plan assets, end of the year	2.5	3.7
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					3.00%
Other Postretirement Benefits Plan [Member] | International equity [Member] | Westar Energy Inc [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	16.2
Fair value of plan assets, end of the year	14	16.2
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					13.00%
Other Postretirement Benefits Plan [Member] | International equity [Member] | KCPL [Member]
Change in plan assets
Fair value of plan assets, end of the year	0.9
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					0.00%
Other Postretirement Benefits Plan [Member] | Bonds [Member] | Westar Energy Inc [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					35.00%
Other Postretirement Benefits Plan [Member] | Bonds [Member] | KCPL [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					85.00%
Other Postretirement Benefits Plan [Member] | Mortgage & asset-backed securities [Member] | Westar Energy Inc [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					0.00%
Other Postretirement Benefits Plan [Member] | Mortgage & asset-backed securities [Member] | KCPL [Member]
Change in plan assets
Fair value of plan assets, beginning of the year	3.6
Fair value of plan assets, end of the year	$ 2.5	$ 3.6
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					4.00%
Other Postretirement Benefits Plan [Member] | Real estate investments [Member] | Westar Energy Inc [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					0.00%
Other Postretirement Benefits Plan [Member] | Real estate investments [Member] | KCPL [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					0.00%
Other Postretirement Benefits Plan [Member] | Other investments | Westar Energy Inc [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					0.00%
Other Postretirement Benefits Plan [Member] | Other investments | KCPL [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage					8.00%
Jointly Owned Nuclear Power Plant [Member]
Defined Benefit Plan Disclosure [Line Items]
Jointly owned utility plant, proportionate ownership share				94.00%	94.00%
Jointly Owned Nuclear Power Plant [Member] | Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Jointly owned utility plant, proportionate ownership share				47.00%	47.00%
Jointly Owned Nuclear Power Plant [Member] | KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Jointly owned utility plant, proportionate ownership share				47.00%	47.00%

Equity Compensation (Details)

Equity Compensation (Details) $ / shares in Units, $ in Millions	Jun. 04, 2018USD ($)shares	Dec. 31, 2018USD ($)$ / sharesRateshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost | $		$ 14.6
Equity compensation expense | $		30.7	$ 8.9	$ 9.2
Income tax benefit | $		$ 1.4	$ 3.5	$ 3.7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Ending balance (in shares)	204,825
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)		255,964
Granted (in shares)		222,465
Converted Great Plains Energy award upon merger (in shares)		82,331
Vested (in shares)		(342,599)
Forfeited (in shares)		(905)
Ending balance (in shares)		217,256	255,964
Weighted average beginning balance (in dollars per share) | $ / shares		$ 46.09
Weighted average granted (in dollars per share) | $ / shares		52.16	$ 53.25	$ 46.35
Weighted average converted (in dollars per share) | $ / shares		53.77
Weighted average vested (in dollars per share) | $ / shares		46.81
Weighted average forfeited (in dollars per share) | $ / shares		50.73
Weighted average ending balance (in dollars per share) | $ / shares		$ 54.07	$ 46.09
Total unrecognized compensation expense | $		$ 7.8
Total fair value of shares vested | $		$ 16	$ 6.1	$ 5.2
Remaining weighted-average contractual term (in years)		1 year 4 months 15 days
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum (in hundredths) | Rate		16.60%
Expected volatility, maximum (in hundredths) | Rate		18.50%
Expected dividend yield (in hundredths) | Rate		2.96%
Risk-free interest rate, minimum (in hundredths) | Rate		1.80%
Risk-free interest rate, maximum (in hundredths) | Rate		2.60%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)		0
Converted Great Plains Energy award upon merger (in shares)		351,708
Forfeited (in shares)		(3,212)
Ending balance (in shares)		348,496	0
Weighted average beginning balance (in dollars per share) | $ / shares		$ 0
Weighted average converted (in dollars per share) | $ / shares		63.79
Weighted average forfeited (in dollars per share) | $ / shares		63.44
Weighted average ending balance (in dollars per share) | $ / shares		$ 63.80	$ 0
Total unrecognized compensation expense | $		$ 6.6
Remaining weighted-average contractual term (in years)		1 year
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)		0
Converted Great Plains Energy award upon merger (in shares)		122,505
Vested (in shares)		(4,760)
Forfeited (in shares)		(1,070)
Ending balance (in shares)		116,675	0
Weighted average beginning balance (in dollars per share) | $ / shares		$ 0
Weighted average converted (in dollars per share) | $ / shares		54.05
Weighted average vested (in dollars per share) | $ / shares		54.50
Weighted average forfeited (in dollars per share) | $ / shares		54.04
Weighted average ending balance (in dollars per share) | $ / shares		$ 54.03	$ 0
Total unrecognized compensation expense | $		$ 2.6
Total fair value of shares vested | $		$ 0.3
Remaining weighted-average contractual term (in years)		1 year 2 months 10 days
Westar Energy Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity compensation expense | $		$ 24.8	$ 8.9	9.2
Income tax benefit | $		1.4	3.5	3.7
KCPL [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity compensation expense | $		6.5	4.2	3.2
Income tax benefit | $		$ 0.1	$ 1.6	$ 1
Great Plains Energy [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exchange ratio	0.5981
Stock Compensation Plan [Member] | Great Plains Energy [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares issued | $	$ 12.5

Short-term Borrowings and Sho_3

Short-term Borrowings and Short-term Bank Lines of Credit (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 1,737.3
Line of Credit Facility, Current Borrowing Capacity	2,500
Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit	738.6
Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	24.1
Master Credit Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,500
Long-term Line of Credit	$ 0
Credit facility expiration date	Dec. 31, 2023
Evergy [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 449	$ 691.8
Line of Credit Facility, Interest Rate at Period End	0.00%	1.83%
Line of Credit Facility, Current Borrowing Capacity	$ 450	$ 979.3
Evergy [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit		275.7
Evergy [Member] | Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	1	11.8
Evergy [Member] | Master Credit Facility [Member]
Short-term Debt [Line Items]
Debt Instrument, Debt Default, Threshold	100
Long-term Line of Credit	$ 0	0
Line of Credit Facility, Covenant Terms	A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance	in compliance
Evergy [Member] | Master Credit Facility [Member] | Maximum [Member]
Short-term Debt [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
KCPL [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 420.4	$ 429.8
Line of Credit Facility, Interest Rate at Period End	2.95%	1.95%
Line of Credit Facility, Current Borrowing Capacity	$ 600	$ 600
KCPL [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit	176.9	167.5
KCPL [Member] | Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	2.7	2.7
KCPL [Member] | Master Credit Facility [Member]
Short-term Debt [Line Items]
Debt Instrument, Debt Default, Threshold	100
Long-term Line of Credit	$ 0	0
Line of Credit Facility, Covenant Terms	A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance	in compliance
KCPL [Member] | Master Credit Facility [Member] | Maximum [Member]
Short-term Debt [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Westar Energy Inc [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 570	$ 691.8
Line of Credit Facility, Interest Rate at Period End	3.08%	1.83%
Line of Credit Facility, Current Borrowing Capacity	$ 1,000	$ 979.3
Westar Energy Inc [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit	411.7	275.7
Westar Energy Inc [Member] | Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	18.3	11.8
Westar Energy Inc [Member] | Master Credit Facility [Member]
Short-term Debt [Line Items]
Debt Instrument, Debt Default, Threshold	100
Long-term Line of Credit	$ 0	0
Line of Credit Facility, Covenant Terms	A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance	in compliance
Westar Energy Inc [Member] | Master Credit Facility [Member] | Maximum [Member]
Short-term Debt [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Kcpl Greater Missouri Operations Member
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 297.9
Line of Credit Facility, Interest Rate at Period End	3.00%
Line of Credit Facility, Current Borrowing Capacity	$ 450
Kcpl Greater Missouri Operations Member | Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit	150
Kcpl Greater Missouri Operations Member | Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	2.1
Kcpl Greater Missouri Operations Member | Master Credit Facility [Member]
Short-term Debt [Line Items]
Debt Instrument, Debt Default, Threshold	100
Long-term Line of Credit	$ 0
Line of Credit Facility, Covenant Terms	A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance	in compliance
Kcpl Greater Missouri Operations Member | Master Credit Facility [Member] | Maximum [Member]
Short-term Debt [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Wester Energy Revolving Credit Facility One [Member] | Westar Energy Inc [Member] | Master Credit Facility [Member]
Short-term Debt [Line Items]
Line Of Credit, Expired		20.7
Line of Credit Facility, Current Borrowing Capacity		730
Wester Energy Revolving Credit Facility Two [Member] | Westar Energy Inc [Member] | Master Credit Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Current Borrowing Capacity		$ 270

Long-Term Debt (Details)

Long-Term Debt (Details) - USD ($) $ in Millions	1 Months Ended			12 Months Ended
	Dec. 31, 2018	Jul. 31, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Current maturities	$ (705.4)			$ (705.4)	$ 0
Unamortized discount and premium, net and debt issuance costs	(57.2)			(57.2)	(39.3)
Long-term debt, net	6,636.3			6,636.3	3,687.6
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	701.1			701.1
Long-term Debt, Maturities, Repayments of Principal in Year Two	251.1			251.1
Long-term Debt, Maturities, Repayments of Principal in Year Three	432			432
Long-term Debt, Maturities, Repayments of Principal in Year Four	287.5			287.5
Long-term Debt, Maturities, Repayments of Principal in Year Five	439.5			439.5
Long-Term debt fair value adjustment [Member]
Debt Instrument [Line Items]
Long-term debt gross	144.8			144.8
Current maturities	(4.3)			(4.3)
Secured Debt [Member] | Mortgage Bonds Due 2020 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 250			$ 250	$ 250
Maturity date				Dec. 31, 2020	Dec. 31, 2020
Interest rates (in hundredths)	5.10%			5.10%	5.10%
Secured Debt [Member] | Mortgage Bonds Due 2025 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 250			$ 250	$ 250
Maturity date				Dec. 31, 2025	Dec. 31, 2025
Interest rates (in hundredths)	3.25%			3.25%	3.25%
Secured Debt [Member] | Mortgage Bonds Due 2026 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 350			$ 350	$ 350
Maturity date				Dec. 31, 2026	Dec. 31, 2026
Interest rates (in hundredths)	2.55%			2.55%	2.55%
Secured Debt [Member] | Mortgage Bonds Due 2027 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 300			$ 300	$ 300
Maturity date				Dec. 31, 2027	Dec. 31, 2027
Interest rates (in hundredths)	3.10%			3.10%	3.10%
Secured Debt [Member] | Mortgage Bonds Due 2042 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 550			$ 550	$ 550
Maturity date				Dec. 31, 2042	Dec. 31, 2042
Interest rates (in hundredths)	4.125%			4.125%	4.125%
Secured Debt [Member] | Mortgage Bonds Due 2043A WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 430			$ 430	$ 430
Maturity date				Dec. 31, 2043	Dec. 31, 2043
Interest rates (in hundredths)	4.10%			4.10%	4.10%
Secured Debt [Member] | Mortgage Bonds Due 2043B WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 250			$ 250	$ 250
Maturity date				Dec. 31, 2043	Dec. 31, 2043
Interest rates (in hundredths)	4.625%			4.625%	4.625%
Secured Debt [Member] | Mortgage Bonds Due 2045 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 300			$ 300	$ 300
Maturity date				Dec. 31, 2045	Dec. 31, 2045
Interest rates (in hundredths)	4.25%			4.25%	4.25%
Secured Debt [Member] | Mortgage Bonds Due 2019 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 300			$ 300	$ 300
Maturity date				Dec. 31, 2019	Dec. 31, 2019
Interest rates (in hundredths)	6.70%			6.70%	6.70%
Secured Debt [Member] | Mortgage Bonds Due 2023 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 50			$ 50	$ 50
Maturity date				Dec. 31, 2023	Dec. 31, 2023
Interest rates (in hundredths)	6.15%			6.15%	6.15%
Secured Debt [Member] | Mortgage Bonds Due 2037 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 175			$ 175	$ 175
Maturity date				Dec. 31, 2037	Dec. 31, 2037
Interest rates (in hundredths)	6.53%			6.53%	6.53%
Secured Debt [Member] | Mortgage Bonds Due 2038 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 100			$ 100	$ 100
Maturity date				Dec. 31, 2038	Dec. 31, 2038
Interest rates (in hundredths)	6.64%			6.64%	6.64%
Secured Debt [Member] | Mortgage Bonds Due 2044 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 250			$ 250	$ 250
Maturity date				Dec. 31, 2044	Dec. 31, 2044
Interest rates (in hundredths)	4.30%			4.30%	4.30%
Secured Debt [Member] | General Mortgage Bonds EIRR Due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 79.5			$ 79.5	$ 0
Maturity date				Dec. 31, 2023	Dec. 31, 2023
Interest rates (in hundredths)	2.95%			2.95%
Secured Debt [Member] | General Mortgage bonds Series 2009A due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 400			$ 400	$ 0
Maturity date				Dec. 31, 2019	Dec. 31, 2019
Interest rates (in hundredths)	7.15%			7.15%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)	8.59%			8.59%
Secured Debt [Member] | First Mortgage Bonds due through 2021 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 3.4			$ 3.4
Debt Instrument Maturity Date Range Start				Dec. 31, 2019
Debt Instrument Maturity Date Range End				Dec. 31, 2021
Interest rates (in hundredths)	9.44%			9.44%
Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032A WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 45			$ 45	$ 45
Maturity date				Dec. 31, 2032	Dec. 31, 2032
Interest rates (in hundredths)	2.46%			2.46%	1.92%
Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032B WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 30.5			$ 30.5	$ 30.5
Maturity date				Dec. 31, 2032	Dec. 31, 2032
Interest rates (in hundredths)	2.46%			2.46%	1.94%
Pollution Control Bonds [Member] | Pollution Control Bonds Due 2027 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 21.9			$ 21.9	$ 21.9
Maturity date				Dec. 31, 2027	Dec. 31, 2027
Interest rates (in hundredths)	2.46%			2.46%	2.00%
Pollution Control Bonds [Member] | Pollution Control Bonds Due 2031 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 50			$ 50	$ 50
Maturity date				Dec. 31, 2031	Dec. 31, 2031
Interest rates (in hundredths)	2.50%			2.50%	2.50%
Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032A KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 14.5			$ 14.5	$ 14.5
Maturity date				Dec. 31, 2032	Dec. 31, 2032
Interest rates (in hundredths)	2.46%			2.46%	2.00%
Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032B KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 10			$ 10	$ 10
Maturity date				Dec. 31, 2032	Dec. 31, 2032
Interest rates (in hundredths)	2.46%			2.46%	2.00%
Pollution Control Bonds [Member] | EIRR Bonds Series 2007A and 2007B due 2035 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 146.5			$ 146.5	$ 0
Maturity date				Dec. 31, 2035	Dec. 31, 2035
Interest rates (in hundredths)	1.865%			1.865%
Pollution Control Bonds [Member] | EIRR bonds 2.875 percent Series 2008 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 23.4			$ 23.4	$ 0
Maturity date				Dec. 31, 2038	Dec. 31, 2038
Interest rates (in hundredths)	2.75%			2.75%
Senior Notes [Member] | Senior notes due 2018 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross					$ 0
Maturity date					Dec. 31, 2018
Senior Notes [Member] | Senior Notes due 2023 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 300			$ 300	$ 0
Maturity date				Dec. 31, 2023	Dec. 31, 2023
Interest rates (in hundredths)	3.15%			3.15%
Senior Notes [Member] | Senior Notes due 2025 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 350			$ 350	$ 0
Maturity date				Dec. 31, 2025	Dec. 31, 2025
Interest rates (in hundredths)	3.65%			3.65%
Senior Notes [Member] | Senior notes due 2035 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 250			$ 250	$ 0
Maturity date				Dec. 31, 2035	Dec. 31, 2035
Interest rates (in hundredths)	6.05%			6.05%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)	5.78%			5.78%
Senior Notes [Member] | Senior Notes Due 2041 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 400			$ 400	$ 0
Maturity date				Dec. 31, 2041	Dec. 31, 2041
Interest rates (in hundredths)	5.30%			5.30%
Senior Notes [Member] | Senior Notes Due 2047 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 300			$ 300	$ 0
Maturity date				Dec. 31, 2047	Dec. 31, 2047
Interest rates (in hundredths)	4.20%			4.20%
Senior Notes [Member] | Senior Notes Due 2048 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 300			$ 300
Maturity date				Dec. 31, 2048
Interest rates (in hundredths)	4.20%			4.20%
Senior Notes [Member] | Senior notes 8.27 percent series due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 80.9			$ 80.9
Maturity date				Dec. 31, 2021
Interest rates (in hundredths)	8.27%			8.27%
Senior Notes [Member] | Senior Notes Series A due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 36			$ 36
Maturity date				Dec. 31, 2025
Interest rates (in hundredths)	3.49%			3.49%
Senior Notes [Member] | Senior Notes Series B due 2033 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 60			$ 60
Maturity date				Dec. 31, 2033
Interest rates (in hundredths)	4.06%			4.06%
Senior Notes [Member] | Senior Notes Series C due 2043 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 150			$ 150
Maturity date				Dec. 31, 2043
Interest rates (in hundredths)	4.74%			4.74%
Senior Notes [Member] | Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 350			$ 350
Maturity date				Dec. 31, 2021
Interest rates (in hundredths)	4.85%			4.85%
Senior Notes [Member] | Senior Notes 5.292 Percent Series Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 287.5			$ 287.5
Maturity date				Dec. 31, 2022
Interest rates (in hundredths)	5.292%			5.292%
Medium-term Notes [Member] | Medium term notes 7.33 percent series due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 3			$ 3
Maturity date				Dec. 31, 2023
Interest rates (in hundredths)	7.33%			7.33%
Medium-term Notes [Member] | Medium term notes 7.17 percent series due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 7			$ 7
Maturity date				Dec. 31, 2023
Interest rates (in hundredths)	7.17%			7.17%
Variable Interest Entities [Member]
Debt Instrument [Line Items]
Current maturities	$ (30.3)			$ (30.3)	$ (28.5)
Long-term debt, net	51.1			51.1	81.4
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	30.3			30.3
Long-term Debt, Maturities, Repayments of Principal in Year Two	32.3			32.3
Long-term Debt, Maturities, Repayments of Principal in Year Three	18.8			18.8
Long-term Debt, Maturities, Repayments of Principal in Year Four	0			0
Long-term Debt, Maturities, Repayments of Principal in Year Five	0			0
Variable Interest Entities [Member] | Unsecured Debt [Member] | Unsecured Debt Due 2021 VIE [Member]
Debt Instrument [Line Items]
Long-term debt gross	81.4			81.4	109.9
Current maturities	(30.3)			(30.3)	(28.5)
Long-term debt, net	51.1			51.1	81.4
Westar Energy Inc [Member]
Debt Instrument [Line Items]
Current maturities	(300)			(300)	0
Unamortized discount and premium, net and debt issuance costs	(37.1)			(37.1)	(39.3)
Long-term debt, net	3,389.8			3,389.8	3,687.6
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	300			300
Long-term Debt, Maturities, Repayments of Principal in Year Two	250			250
Long-term Debt, Maturities, Repayments of Principal in Year Three	0			0
Long-term Debt, Maturities, Repayments of Principal in Year Four	0			0
Long-term Debt, Maturities, Repayments of Principal in Year Five	50			50
Westar Mortgage Bonds [Abstract]
Additional Principal First Mortgage Bonds Available To Be Issued				344.5
Maximum Amount Of First Mortgage Bonds Authorized	3,500			3,500
Westar Energy Inc [Member] | Long-Term debt fair value adjustment [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2020 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	250			250	250
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2025 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	250			250	250
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2026 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	350			350	350
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2027 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	300			300	300
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2042 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	550			550	550
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2043A WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	430			430	430
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2043B WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	250			250	250
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2045 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	300			300	300
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2019 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	300			300	300
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2023 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	50			50	50
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2037 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	175			175	175
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2038 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	100			100	100
Westar Energy Inc [Member] | Secured Debt [Member] | Mortgage Bonds Due 2044 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	250			250	250
Westar Energy Inc [Member] | Secured Debt [Member] | General Mortgage Bonds EIRR Due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
Westar Energy Inc [Member] | Secured Debt [Member] | General Mortgage bonds Series 2009A due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
Westar Energy Inc [Member] | Secured Debt [Member] | First Mortgage Bonds due through 2021 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032A WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 45			45	45
Maturity date	Dec. 31, 2032
Debt Instrument, Face Amount	$ 45			45
Westar Energy Inc [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032B WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	30.5			30.5	30.5
Debt Instrument, Face Amount	30.5			30.5
Westar Energy Inc [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2027 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	21.9			21.9	21.9
Debt Instrument, Face Amount	21.9			21.9
Westar Energy Inc [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2031 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	50			50	50
Westar Energy Inc [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032A KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	14.5			14.5	14.5
Debt Instrument, Face Amount	14.5			14.5
Westar Energy Inc [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032B KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	10			10	10
Debt Instrument, Face Amount	10			10
Westar Energy Inc [Member] | Pollution Control Bonds [Member] | EIRR Bonds Series 2007A and 2007B due 2035 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
Westar Energy Inc [Member] | Pollution Control Bonds [Member] | EIRR bonds 2.875 percent Series 2008 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior notes due 2018 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross					0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes due 2023 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes due 2025 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior notes due 2035 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes Due 2041 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes Due 2047 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes Due 2048 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior notes 8.27 percent series due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes Series A due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes Series B due 2033 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes Series C due 2043 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Senior Notes [Member] | Senior Notes 5.292 Percent Series Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Medium-term Notes [Member] | Medium term notes 7.33 percent series due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Medium-term Notes [Member] | Medium term notes 7.17 percent series due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
Westar Energy Inc [Member] | Variable Interest Entities [Member]
Debt Instrument [Line Items]
Current maturities	(30.3)			(30.3)	(28.5)
Long-term debt, net	51.1			51.1	81.4
Westar Energy Inc [Member] | Variable Interest Entities [Member] | Unsecured Debt [Member] | Unsecured Debt Due 2021 VIE [Member]
Debt Instrument [Line Items]
Long-term debt gross	81.4			81.4	109.9
Current maturities	(30.3)			(30.3)	(28.5)
Long-term debt, net	$ 51.1			51.1	81.4
Kansas Gas And Electric Company [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032A WR [Member]
Debt Instrument [Line Items]
Maturity date	Dec. 31, 2032
Kansas Gas And Electric Company [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2027 KGE [Member]
Debt Instrument [Line Items]
Maturity date	Dec. 31, 2027
Kansas Gas And Electric Company [Member] | Unsecured Debt [Member] | Pollution Control Bonds Due 2032B WR [Member]
Debt Instrument [Line Items]
Maturity date	Dec. 31, 2032
KCPL [Member]
Debt Instrument [Line Items]
Current maturities	$ (400)			(400)	(350)
Unamortized discount and premium, net and debt issuance costs	(19.3)			(19.3)	(17.2)
Long-term debt, net	2,130.1			2,130.1	2,232.2
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	400			400
Long-term Debt, Maturities, Repayments of Principal in Year Two	0			0
Long-term Debt, Maturities, Repayments of Principal in Year Three	0			0
Long-term Debt, Maturities, Repayments of Principal in Year Four	0			0
Long-term Debt, Maturities, Repayments of Principal in Year Five	379.5			379.5
KCPL [Member] | Long-Term debt fair value adjustment [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2020 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2025 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2026 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2027 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2042 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2043A WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2043B WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2045 WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2019 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2023 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2037 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2038 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | Mortgage Bonds Due 2044 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Secured Debt [Member] | General Mortgage Bonds EIRR Due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt gross	79.5			79.5	79.5
EIRR bonds repurchased and held	21.9			21.9	$ 21.9
Interest rates (in hundredths)					2.95%
KCPL [Member] | Secured Debt [Member] | General Mortgage bonds Series 2009A due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt gross	400			400	$ 400
Interest rates (in hundredths)					7.15%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)					8.59%
KCPL [Member] | Secured Debt [Member] | First Mortgage Bonds due through 2021 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
KCPL [Member] | Secured Debt [Member] | General Mortgage bonds EIRR series 2005 [Member]
Debt Instrument [Line Items]
EIRR bonds repurchased and held	50			50	$ 50
KCPL [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032A WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032B WR [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2027 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2031 KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032A KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Pollution Control Bonds [Member] | Pollution Control Bonds Due 2032B KGE [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0	0
KCPL [Member] | Pollution Control Bonds [Member] | EIRR Bonds Series 2007A and 2007B due 2035 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 146.5			146.5	$ 146.5
Maturity date	Dec. 31, 2035
Interest rates (in hundredths)					1.329%
Debt Instrument, Face Amount	$ 146.5			146.5
KCPL [Member] | Pollution Control Bonds [Member] | EIRR bonds 2.875 percent Series 2008 [Member]
Debt Instrument [Line Items]
Long-term debt gross	23.4			23.4	$ 23.4
Maturity date		Dec. 31, 2038
Interest rates (in hundredths)		2.75%			2.875%
Debt Instrument, Face Amount		$ 23.4
KCPL [Member] | Senior Notes [Member] | Senior notes due 2018 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross					$ 350
Interest rates (in hundredths)			6.375%		6.375%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)					7.49%
Repayments of long-term debt			$ 350
KCPL [Member] | Senior Notes [Member] | Senior Notes due 2023 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	300			300	$ 300
Interest rates (in hundredths)					3.15%
KCPL [Member] | Senior Notes [Member] | Senior Notes due 2025 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	350			350	$ 350
Interest rates (in hundredths)					3.65%
KCPL [Member] | Senior Notes [Member] | Senior notes due 2035 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	250			250	$ 250
Interest rates (in hundredths)					6.05%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)					5.78%
KCPL [Member] | Senior Notes [Member] | Senior Notes Due 2041 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	400			400	$ 400
Interest rates (in hundredths)					5.30%
KCPL [Member] | Senior Notes [Member] | Senior Notes Due 2047 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	300			300	$ 300
Interest rates (in hundredths)					4.20%
KCPL [Member] | Senior Notes [Member] | Senior Notes Due 2048 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	300		$ 300	300
Maturity date			Dec. 31, 2048
Interest rates (in hundredths)			4.20%
KCPL [Member] | Senior Notes [Member] | Senior notes 8.27 percent series due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
KCPL [Member] | Senior Notes [Member] | Senior Notes Series A due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
KCPL [Member] | Senior Notes [Member] | Senior Notes Series B due 2033 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
KCPL [Member] | Senior Notes [Member] | Senior Notes Series C due 2043 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
KCPL [Member] | Senior Notes [Member] | Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
KCPL [Member] | Senior Notes [Member] | Senior Notes 5.292 Percent Series Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
KCPL [Member] | Medium-term Notes [Member] | Medium term notes 7.33 percent series due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt gross	0			0
KCPL [Member] | Medium-term Notes [Member] | Medium term notes 7.17 percent series due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 0			$ 0
KCPL Greater Missouri Operations [Member] | Senior Notes [Member] | Senior Notes Series A due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchase Amount		89
GMO Senior Notes [Abstract]
Debt Instrument, Covenant Description				GMO is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the agreement, not greater than 0.65 to 1.00. In addition, GMO's priority debt, as defined in the agreement, cannot exceed 15% of consolidated tangible net worth, as defined in the agreement.
Debt Instrument, Covenant Compliance				in compliance
KCPL Greater Missouri Operations [Member] | Senior Notes [Member] | Senior Notes Series B due 2033 [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchase Amount		$ 15
GMO Senior Notes [Abstract]
Debt Instrument, Covenant Description				GMO is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the agreement, not greater than 0.65 to 1.00 at all times. In addition, GMO's priority debt, as defined in the agreement, cannot exceed 15% of consolidated tangible net worth, as defined in the agreement.
Debt Instrument, Covenant Compliance				in compliance
KCPL Greater Missouri Operations [Member] | Senior Notes [Member] | Senior Notes Series C due 2043 [Member]
GMO Senior Notes [Abstract]
Debt Instrument, Covenant Description				GMO is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the agreement, not greater than 0.65 to 1.00 at all times. In addition, GMO's priority debt, as defined in the agreement, cannot exceed 15% of consolidated tangible net worth, as defined in the agreement.
Debt Instrument, Covenant Compliance				in compliance

Fair Value Measurements - Debt

Fair Value Measurements - Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount	$ 500
Derivative, Fair Value, Net	5.4
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	(5.4)	$ 0	$ 0
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	7,341.7	3,687.6
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Variable Interest Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	81.4	109.9
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	7,412.1	4,010.6
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Variable Interest Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	81.3	110.8
Westar Energy Inc [Member] | Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	3,689.8	3,687.6
Westar Energy Inc [Member] | Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Variable Interest Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	81.4	109.9
Westar Energy Inc [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	3,771.3	4,010.6
Westar Energy Inc [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Variable Interest Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	81.3	110.8
KCPL [Member] | Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	2,530.1	2,582.2
KCPL [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	2,637.5	$ 2,799.1
Long-Term debt fair value adjustment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Gross	144.8
Long-Term debt fair value adjustment [Member] | Westar Energy Inc [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Gross	0
Long-Term debt fair value adjustment [Member] | KCPL [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Gross	$ 0

Fair Value Measurements - Recur

Fair Value Measurements - Recurring (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets [Abstract]
Derivative, Fair Value, Net	$ 5.4
Decommissioning Trust Assets [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	42.6
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Total	528.3	$ 271.4
Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	227.5	237.1
Total rabbi trust	30.6	34.3
Total	258.1	271.4
Fair Value, Measurements, Recurring [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	244.6	258.4
Total self-insured health plan trust	12.4	10.9
Total	257	269.3
Fair Value, Measurements, Recurring [Member] | Other Evergy [Member]
Assets [Abstract]
Total rabbi trust	13.2
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	166.6	183.8
Total self-insured health plan trust	0.5	0.5
Fair Value, Measurements, Recurring [Member] | Core Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	37.5	33.3
Total rabbi trust	24.8	27.3
Fair Value, Measurements, Recurring [Member] | High-Yield Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	18.9	18.1
Fair Value, Measurements, Recurring [Member] | Emerging Markets Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	15.4	17.3
Fair Value, Measurements, Recurring [Member] | Debt Equity Other Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	12.9	14.1
Total rabbi trust	5.6	6.8
Fair Value, Measurements, Recurring [Member] | Alternative Investment Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	24.1	21.7
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	11.8	10.8
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total self-insured health plan trust	3.9	2.7
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	42.1	35.3
Fair Value, Measurements, Recurring [Member] | US Government Corporations and Agencies Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0.4	0.4
Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	2.1	2.1
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	30.9	34.1
Fair Value, Measurements, Recurring [Member] | Debt Security, Government, Non-US [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0.1	0.1
Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0.1	0.1
Total rabbi trust	0.2	0.2
Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	1.7	2.5
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Assets [Abstract]
Total self-insured health plan trust	8	7.7
Fair Value, Measurements, Recurring [Member] | Commodity Contract [Member]
Assets [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	5.4
Fair Value, Measurements, Recurring [Member] | Commodity Contract [Member] | Other Evergy [Member]
Assets [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	5.4
Fair Value, Measurements, Recurring [Member] | Other Trust Assets [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0.7	0.1
Fair Value, Measurements, Recurring [Member] | Decommissioning Trust Assets [Member]
Assets [Abstract]
Total nuclear decommissioning trust	472.1	237.1
Level 2 transferred to Level 1		199.4
Fair Value, Measurements, Recurring [Member] | Rabbi Trusts [Member]
Assets [Abstract]
Total rabbi trust	43.8	34.3
Level 2 transferred to NAV		34.1
Fair Value, Measurements, Recurring [Member] | Self-Insured Health Plan Trust [Member]
Assets [Abstract]
Total self-insured health plan trust	12.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets [Abstract]
Total	405	0.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	184.9	0.1
Total rabbi trust	0.2	0.2
Total	185.1	0.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	211.1	221.7
Total self-insured health plan trust	8.8	8.5
Total	219.9	230.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Evergy [Member]
Assets [Abstract]
Total rabbi trust	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	166.6	183.8
Total self-insured health plan trust	0.5	0.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Core Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	37.5	0
Total rabbi trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | High-Yield Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	18.9	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Emerging Markets Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	15.4	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Debt Equity Other Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	12.9	0
Total rabbi trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Alternative Investment Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Real Estate Funds [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total self-insured health plan trust	0.3	0.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury and Government [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	42.1	35.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Corporations and Agencies Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Debt Security, Government, Non-US [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0.1	0.1
Total rabbi trust	0.2	0.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	1.7	2.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Assets [Abstract]
Total self-insured health plan trust	8	7.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Trust Assets [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0.7	0.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Decommissioning Trust Assets [Member]
Assets [Abstract]
Total nuclear decommissioning trust	396	0.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Rabbi Trusts [Member]
Assets [Abstract]
Total rabbi trust	0.2	0.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Self-Insured Health Plan Trust [Member]
Assets [Abstract]
Total self-insured health plan trust	8.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Total	37.1	233.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	199.4
Total rabbi trust	0	34.1
Total	0	233.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	33.5	36.7
Total self-insured health plan trust	3.6	2.4
Total	37.1	39.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Evergy [Member]
Assets [Abstract]
Total rabbi trust	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Total self-insured health plan trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Core Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	33.3
Total rabbi trust	0	27.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | High-Yield Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	18.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Emerging Markets Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	17.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Equity Other Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	14.1
Total rabbi trust	0	6.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Alternative Investment Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Real Estate Funds [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total self-insured health plan trust	3.6	2.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury and Government [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Corporations and Agencies Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0.4	0.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	2.1	2.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	30.9	34.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Security, Government, Non-US [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0.1	0.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Cash Equivalents [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Total rabbi trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Cash Equivalents [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Assets [Abstract]
Total self-insured health plan trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodity Contract [Member]
Assets [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	5.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodity Contract [Member] | Other Evergy [Member]
Assets [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	5.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Trust Assets [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Decommissioning Trust Assets [Member]
Assets [Abstract]
Total nuclear decommissioning trust	33.5	199.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trusts [Member]
Assets [Abstract]
Total rabbi trust	0	34.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Self-Insured Health Plan Trust [Member]
Assets [Abstract]
Total self-insured health plan trust	3.6
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets [Abstract]
Total	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Total rabbi trust	0	0
Total	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Total self-insured health plan trust	0	0
Total	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Evergy [Member]
Assets [Abstract]
Total rabbi trust	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Total self-insured health plan trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Core Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Total rabbi trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | High-Yield Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Emerging Markets Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Debt Equity Other Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Total rabbi trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Alternative Investment Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Real Estate Funds [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total self-insured health plan trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury and Government [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Corporations and Agencies Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Debt Security, Government, Non-US [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cash Equivalents [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Total rabbi trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cash Equivalents [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member] | KCPL [Member]
Assets [Abstract]
Total self-insured health plan trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Trust Assets [Member] | KCPL [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Decommissioning Trust Assets [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Rabbi Trusts [Member]
Assets [Abstract]
Total rabbi trust	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Self-Insured Health Plan Trust [Member]
Assets [Abstract]
Total self-insured health plan trust	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Assets [Abstract]
Total	86.2	37.6
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	42.6	37.6
Total rabbi trust	30.4	0
Total	73	37.6
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Other Evergy [Member]
Assets [Abstract]
Total rabbi trust	13.2	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Core Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0
Total rabbi trust	24.8	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | High-Yield Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Emerging Markets Bond Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Debt Equity Other Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0
Total rabbi trust	5.6	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Alternative Investment Fund [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	24.1	21.7
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Real Estate Funds [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	11.8	10.8
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Cash Equivalents [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0
Total rabbi trust	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Decommissioning Trust Assets [Member]
Assets [Abstract]
Total nuclear decommissioning trust	42.6	37.6
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Rabbi Trusts [Member]
Assets [Abstract]
Total rabbi trust	43.6	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Self-Insured Health Plan Trust [Member]
Assets [Abstract]
Total self-insured health plan trust	0
Geographic Distribution, Domestic [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	70.6	73.8
Geographic Distribution, Domestic [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	63.9	0
Geographic Distribution, Domestic [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	68.7
Geographic Distribution, Domestic [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	0
Geographic Distribution, Domestic [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	6.7	5.1
Geographic Distribution, Foreign [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	36.2	47.9
Geographic Distribution, Foreign [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	36.2	0
Geographic Distribution, Foreign [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	47.9
Geographic Distribution, Foreign [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	0	$ 0
Geographic Distribution, Foreign [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Equity Securities [Member] | Westar Energy Inc [Member]
Assets [Abstract]
Total nuclear decommissioning trust	$ 0

Fair Value Measurements - NAV (

Fair Value Measurements - NAV (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)fundextension	Dec. 31, 2017USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Unfunded Commitments	$ 4.3	$ 2.8
Westar Energy Inc [Member] | Decommissioning Trust Assets [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	42.6
NAV, Unfunded Commitments	4.3	2.8
Westar Energy Inc [Member] | Alternative Investment Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Unfunded Commitments	$ 0	0
NAV, Length of Settlement	65 days
Westar Energy Inc [Member] | Real Estate Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Unfunded Commitments	$ 0	0
NAV, Length of Settlement	65 days
Westar Energy Inc [Member] | Core Bond Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Unfunded Commitments	$ 0	0
Westar Energy Inc [Member] | Debt Equity Other Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Unfunded Commitments	0	0
Westar Energy Inc [Member] | Rabbi Trusts [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Unfunded Commitments	0	0
Other Evergy [Member] | Rabbi Trusts [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Unfunded Commitments	0	0
Geographic Distribution, Domestic [Member] | Westar Energy Inc [Member] | Equity Securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Unfunded Commitments	$ 4.3	2.8
NAV, Number of funds | fund	5
NAV, Number of funds making distributions | fund	3
Geographic Distribution, Domestic [Member] | Westar Energy Inc [Member] | Equity Securities - Fourth Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Length of Settlement	15 years
NAV, Extension term	1 year
NAV, Number of extensions | extension	3
Geographic Distribution, Domestic [Member] | Westar Energy Inc [Member] | Equity Securities - Fifth Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Length of Settlement	15 years
Fair Value, Measurements, Recurring [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Assets, Fair Value Disclosure	$ 528.3	271.4
Fair Value, Measurements, Recurring [Member] | Decommissioning Trust Assets [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	472.1	237.1
Fair Value, Measurements, Recurring [Member] | Rabbi Trusts [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	43.8	34.3
Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	227.5	237.1
Total rabbi trust	30.6	34.3
Assets, Fair Value Disclosure	258.1	271.4
Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member] | Alternative Investment Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	24.1	21.7
Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member] | Real Estate Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	11.8	10.8
Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member] | Core Bond Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	37.5	33.3
Total rabbi trust	24.8	27.3
Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member] | Debt Equity Other Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	12.9	14.1
Total rabbi trust	5.6	6.8
Fair Value, Measurements, Recurring [Member] | Other Evergy [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	13.2
Fair Value, Measurements, Recurring [Member] | Geographic Distribution, Domestic [Member] | Westar Energy Inc [Member] | Equity Securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	70.6	73.8
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Assets, Fair Value Disclosure	86.2	37.6
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member] | Decommissioning Trust Assets [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	42.6	37.6
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trusts [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	43.6	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	42.6	37.6
Total rabbi trust	30.4	0
Assets, Fair Value Disclosure	73	37.6
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member] | Alternative Investment Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	24.1	21.7
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member] | Real Estate Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	11.8	10.8
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member] | Core Bond Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	0
Total rabbi trust	24.8	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member] | Westar Energy Inc [Member] | Debt Equity Other Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	0
Total rabbi trust	5.6	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member] | Other Evergy [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total rabbi trust	13.2	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Measurements, Recurring [Member] | Geographic Distribution, Domestic [Member] | Westar Energy Inc [Member] | Equity Securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total nuclear decommissioning trust	$ 6.7	$ 5.1

Fair Value Measurements - Gain

Fair Value Measurements - Gain (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	$ (53.6)	$ 1.4	$ 10.4
Decommissioning Trust Assets - Equity [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	(54.1)	15.7	9
Rabbi Trusts [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	1	(14.3)	1.4
Decommissioning Trust Assets - Debt [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	(0.5)	0	0
Westar Energy Inc [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	(30.8)	1.4	10.4
Westar Energy Inc [Member] | Decommissioning Trust Assets - Equity [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	(31.8)	15.7	9
Westar Energy Inc [Member] | Rabbi Trusts [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	1	(14.3)	1.4
KCPL [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	(23.2)	27.2	14.5
KCPL [Member] | Decommissioning Trust Assets - Equity [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	(20.7)	26.7	14.8
KCPL [Member] | Decommissioning Trust Assets - Debt [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	$ (2.5)	$ 0.5	$ (0.3)

Commitments and Contingencies_2

Commitments and Contingencies Commitments and Contingencies Contractual Commitments (Details) $ in Millions	Dec. 31, 2018USD ($)
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	$ 608.7
Unrecorded Unconditional Purchase Obligation, Due within Two Years	430.5
Unrecorded Unconditional Purchase Obligation, Due within Three Years	156.1
Unrecorded Unconditional Purchase Obligation, Due within Four Years	137.3
Unrecorded Unconditional Purchase Obligation, Due within Five Years	137.4
Unrecorded Unconditional Purchase Obligation, Due after Five Years	517.4
Unrecorded Unconditional Purchase Obligation	1,987.4
Fuel [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	423.6
Unrecorded Unconditional Purchase Obligation, Due within Two Years	364.4
Unrecorded Unconditional Purchase Obligation, Due within Three Years	95.3
Unrecorded Unconditional Purchase Obligation, Due within Four Years	82.9
Unrecorded Unconditional Purchase Obligation, Due within Five Years	87.5
Unrecorded Unconditional Purchase Obligation, Due after Five Years	116.2
Unrecorded Unconditional Purchase Obligation	1,169.9
Power [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	47.3
Unrecorded Unconditional Purchase Obligation, Due within Two Years	47.3
Unrecorded Unconditional Purchase Obligation, Due within Three Years	47.4
Unrecorded Unconditional Purchase Obligation, Due within Four Years	47.6
Unrecorded Unconditional Purchase Obligation, Due within Five Years	47.8
Unrecorded Unconditional Purchase Obligation, Due after Five Years	366.8
Unrecorded Unconditional Purchase Obligation	604.2
Other [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	137.8
Unrecorded Unconditional Purchase Obligation, Due within Two Years	18.8
Unrecorded Unconditional Purchase Obligation, Due within Three Years	13.4
Unrecorded Unconditional Purchase Obligation, Due within Four Years	6.8
Unrecorded Unconditional Purchase Obligation, Due within Five Years	2.1
Unrecorded Unconditional Purchase Obligation, Due after Five Years	34.4
Unrecorded Unconditional Purchase Obligation	213.3
Westar Energy Inc [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	328.3
Unrecorded Unconditional Purchase Obligation, Due within Two Years	227
Unrecorded Unconditional Purchase Obligation, Due within Three Years	31.4
Unrecorded Unconditional Purchase Obligation, Due within Four Years	47.9
Unrecorded Unconditional Purchase Obligation, Due within Five Years	46.9
Unrecorded Unconditional Purchase Obligation, Due after Five Years	74.1
Unrecorded Unconditional Purchase Obligation	755.6
Westar Energy Inc [Member] | Fuel [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	240.9
Unrecorded Unconditional Purchase Obligation, Due within Two Years	218.1
Unrecorded Unconditional Purchase Obligation, Due within Three Years	25.9
Unrecorded Unconditional Purchase Obligation, Due within Four Years	45.7
Unrecorded Unconditional Purchase Obligation, Due within Five Years	46.9
Unrecorded Unconditional Purchase Obligation, Due after Five Years	74.1
Unrecorded Unconditional Purchase Obligation	651.6
Westar Energy Inc [Member] | Other [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	87.4
Unrecorded Unconditional Purchase Obligation, Due within Two Years	8.9
Unrecorded Unconditional Purchase Obligation, Due within Three Years	5.5
Unrecorded Unconditional Purchase Obligation, Due within Four Years	2.2
Unrecorded Unconditional Purchase Obligation, Due within Five Years	0
Unrecorded Unconditional Purchase Obligation, Due after Five Years	0
Unrecorded Unconditional Purchase Obligation	104
KCPL [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	232.1
Unrecorded Unconditional Purchase Obligation, Due within Two Years	170.7
Unrecorded Unconditional Purchase Obligation, Due within Three Years	111.3
Unrecorded Unconditional Purchase Obligation, Due within Four Years	76.1
Unrecorded Unconditional Purchase Obligation, Due within Five Years	77.5
Unrecorded Unconditional Purchase Obligation, Due after Five Years	326.3
Unrecorded Unconditional Purchase Obligation	994
KCPL [Member] | Fuel [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	162.6
Unrecorded Unconditional Purchase Obligation, Due within Two Years	126.9
Unrecorded Unconditional Purchase Obligation, Due within Three Years	69.4
Unrecorded Unconditional Purchase Obligation, Due within Four Years	37.2
Unrecorded Unconditional Purchase Obligation, Due within Five Years	40.6
Unrecorded Unconditional Purchase Obligation, Due after Five Years	42.1
Unrecorded Unconditional Purchase Obligation	478.8
KCPL [Member] | Power [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	34.8
Unrecorded Unconditional Purchase Obligation, Due within Two Years	34.8
Unrecorded Unconditional Purchase Obligation, Due within Three Years	34.9
Unrecorded Unconditional Purchase Obligation, Due within Four Years	35.1
Unrecorded Unconditional Purchase Obligation, Due within Five Years	35.3
Unrecorded Unconditional Purchase Obligation, Due after Five Years	254.5
Unrecorded Unconditional Purchase Obligation	429.4
KCPL [Member] | Other [Member]
Purchase Commitments [Abstract]
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	34.7
Unrecorded Unconditional Purchase Obligation, Due within Two Years	9
Unrecorded Unconditional Purchase Obligation, Due within Three Years	7
Unrecorded Unconditional Purchase Obligation, Due within Four Years	3.8
Unrecorded Unconditional Purchase Obligation, Due within Five Years	1.6
Unrecorded Unconditional Purchase Obligation, Due after Five Years	29.7
Unrecorded Unconditional Purchase Obligation	$ 85.8

Commitments and Contingencies E

Commitments and Contingencies Environmental Matters (Details) $ in Millions	Dec. 31, 2018USD ($)
Nuclear Insurance [Abstract]
Industry Aggregate Limit For Nuclear Insurance	$ 3,200
Industry Aggregate Limit For Non Nuclear Insurance	1,800
Nuclear Liability Insurance [Abstract]
Nuclear Liability Insurance, Full Limit Of Public Liability	14,100
Nuclear Liability Insurance, Maximum Available Commercial Insurance	500
Nuclear Liability Insurance, Industry Wide Retrospective Assessment Program	13,600
Nuclear Liability Insurance, Owners Insurance Amount, Maximum	137.6
Nuclear Liability Insurance, Owners Insurance, Amount Per Incident	20.5
Nuclear Liability Insurance, Owners Property Insurance, Maximum	2,800
Nuclear Liability Insurance, Owners Nonnuclear Property Insurance, Maximum	2,300
Nuclear Liability Insurance, Owners Property Insurance Assessment, Maximum	37.4
Evergy [Member]
Nuclear Liability Insurance [Abstract]
Nuclear Liability Insurance, Owners Insurance Amount, Maximum	129.2
Nuclear Liability Insurance, Owners Insurance, Amount Per Incident	19.2
Nuclear Liability Insurance, Owners Property Insurance Assessment, Maximum	35.2
Westar Energy Inc [Member]
Nuclear Liability Insurance [Abstract]
Nuclear Liability Insurance, Owners Insurance Amount, Maximum	64.6
Nuclear Liability Insurance, Owners Insurance, Amount Per Incident	9.6
Nuclear Liability Insurance, Owners Property Insurance Assessment, Maximum	17.6
KCPL [Member]
Nuclear Liability Insurance [Abstract]
Nuclear Liability Insurance, Owners Insurance Amount, Maximum	64.6
Nuclear Liability Insurance, Owners Insurance, Amount Per Incident	9.6
Nuclear Liability Insurance, Owners Property Insurance Assessment, Maximum	$ 17.6

Commitments and Contingencies O

Commitments and Contingencies Operating Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Leases, Rent Expense, Net	$ 24.5	$ 15.7	$ 13.6
2,019	24.2
2,020	20.7
2,021	18.4
2,022	15.2
2,023	12.4
After 2,023	95
Total	185.9
KCPL [Member]
Operating Leases, Rent Expense, Net	11.4	13.1	13.7
2,019	10.2
2,020	10.6
2,021	10.3
2,022	10
2,023	9.6
After 2,023	91.8
Total	142.5
Westar Energy Inc [Member]
Operating Leases, Rent Expense, Net	17.7	$ 15.7	$ 13.6
2,019	14
2,020	10.1
2,021	8.1
2,022	5.2
2,023	2.8
After 2,023	3.1
Total	$ 43.3

Commitments and Contingencies_3

Commitments and Contingencies Capital Leases, Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Capital Leased Assets [Line Items]
Capital Leases, Balance Sheet, Assets by Major Class, Net	$ 162.3	$ 43.6
Accumulated amortization	(160)	(17.1)
Vehicles [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	20.2	19.7
Computer Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	0.2	0.9
Electric Generation Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	296.7	40.1
Other Machinery and Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	5.2	0
Westar Energy Inc [Member]
Capital Leased Assets [Line Items]
Capital Leases, Balance Sheet, Assets by Major Class, Net	40.2	43.6
Accumulated amortization	(20.3)	(17.1)
Westar Energy Inc [Member] | Vehicles [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	20.2	19.7
Westar Energy Inc [Member] | Computer Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	0.2	0.9
Westar Energy Inc [Member] | Electric Generation Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	40.1	40.1
Westar Energy Inc [Member] | Other Machinery and Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	0	0
KCPL [Member]
Capital Leased Assets [Line Items]
Capital Leases, Balance Sheet, Assets by Major Class, Net	1.5	1.5
Accumulated amortization	(1.1)	(1.1)
KCPL [Member] | Vehicles [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	0	0
KCPL [Member] | Computer Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	0	0
KCPL [Member] | Electric Generation Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	0	0
KCPL [Member] | Other Machinery and Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	$ 2.6	$ 2.6

Commitments and Contingencies_4

Commitments and Contingencies Capital Leases, Minimum Annual Rental Payments (Details) $ in Millions	Dec. 31, 2018USD ($)
Capital Leased Assets [Line Items]
2,019	$ 6.4
2,020	5.8
2,021	5.3
2,022	4.7
2,023	4
After 2,023	48.6
Total capital lease payments	74.8
Amounts representing imputed interest	(25.8)
Present value of net minimum lease payments under capital leases	49
Less: current portion	(3.9)
Total long-term obligations under capital leases	45.1
Westar Energy Inc [Member]
Capital Leased Assets [Line Items]
2,019	6
2,020	5.4
2,021	4.9
2,022	4.3
2,023	3.6
After 2,023	46.4
Total capital lease payments	70.6
Amounts representing imputed interest	(24.6)
Present value of net minimum lease payments under capital leases	46
Less: current portion	(3.7)
Total long-term obligations under capital leases	42.3
KCPL [Member]
Capital Leased Assets [Line Items]
2,019	0.2
2,020	0.2
2,021	0.2
2,022	0.2
2,023	0.2
After 2,023	1.1
Total capital lease payments	2.1
Amounts representing imputed interest	(0.6)
Present value of net minimum lease payments under capital leases	1.5
Less: current portion	(0.1)
Total long-term obligations under capital leases	$ 1.4

Guarantees (Details)

Guarantees (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Guarantor Obligations [Line Items]
Origin and purpose	In the ordinary course of business, Evergy and certain of its subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of certain subsidiaries. Such agreements include, for example, guarantees and letters of credit. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to a subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the subsidiary's intended business purposes.
Maximum exposure	$ 111.3
Direct Guarantee [Member]
Guarantor Obligations [Line Items]
Origin and purpose	direct guarantees to GMO counterparties
Maximum exposure	$ 17
Obligations term	expire in 2020
Guarantee of Indebtedness of Others [Member] | Long-term Debt [Member]
Guarantor Obligations [Line Items]
Origin and purpose	guarantee of GMO long-term debt
Maximum exposure	$ 94.3
Obligations term	maturity dates ranging from 2019 to 2023
Guarantee of Indebtedness of Others [Member] | Commercial Paper [Member]
Guarantor Obligations [Line Items]
Origin and purpose	guaranteed GMO's commercial paper program
Maximum exposure	$ 150

Related Party Transactions an_3

Related Party Transactions and Relationships (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Westar Energy Inc [Member] | KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	$ 2.6	$ 0
Westar Energy Inc [Member] | KCPL [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	(13.5)	0
Westar Energy Inc [Member] | KCPL [Member] | Operating Expenses and Capital Costs Billed [Member]
Related Party Transaction [Line Items]
Related party transaction	17.5
Westar Energy Inc [Member] | Evergy [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	(1.4)	0
Westar Energy Inc [Member] | Evergy [Member] | Income Taxes Payable [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	42.7
KCPL [Member] | Money Pool [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	0	0
KCPL [Member] | KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	72.6	65.8
KCPL [Member] | Westar Energy Inc [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	13.5	0
KCPL [Member] | Evergy [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	15.7	0
KCPL [Member] | Evergy [Member] | Income Taxes Payable [Member]
Related Party Transaction [Line Items]
Due to related parties	(2)
KCPL [Member] | Great Plains Energy [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	$ 0	18.9
Iatan No 1 And 2 [Member] | KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Jointly owned utility plant, proportionate ownership share	18.00%
Iatan No 1 And 2 [Member] | KCPL [Member] | KCPL Greater Missouri Operations [Member] | Operating Expenses and Capital Costs Billed [Member]
Related Party Transaction [Line Items]
Related party transaction	$ 183.2	$ 196.3	$ 194.4
Jeffrey Energy Center [Member] | KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Jointly owned utility plant, proportionate ownership share	8.00%
Jeffrey Energy Center [Member] | Westar Energy Inc [Member] | KCPL Greater Missouri Operations [Member] | Operating Expenses and Capital Costs Billed [Member]
Related Party Transaction [Line Items]
Related party transaction	$ 12.3
La Cygne Station [Member] | Westar Energy Inc [Member]
Related Party Transaction [Line Items]
Jointly owned utility plant, proportionate ownership share	50.00%
La Cygne Station [Member] | KCPL [Member] | Westar Energy Inc [Member] | Operating Expenses and Capital Costs Billed [Member]
Related Party Transaction [Line Items]
Related party transaction	$ 82.9

Shareholders' Equity (Details)

Shareholders' Equity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Nov. 01, 2018	Aug. 01, 2018	Jul. 31, 2018	Dec. 31, 2017
Common Shareholders' Equity [Line Items]
Common stock - shares authorized (in shares)	600,000,000				275,000,000
Preferred stock - shares authorized (in shares)	12,000,000
Number of shares authorized to be repurchased (in shares)				60,000,000
Stock Repurchased and Retired During Period, Value	$ 1,042.3
Stock repurchased and retired during period under repurchase plan, value	$ 1,042
Stock Repurchased and Retired During Period, Shares	16,400,000
Accelerated Share Repurchases, Settlement (Payment) or Receipt		$ (475)	$ (450)
Partial Settlement Of Accelerated Share Repurchase Agreement, Shares	6,400,000
Final Settlement Of Accelerated Share Repurchase Agreement Shares	7,900,000
Restriction on payment of dividends, minimum ratio of total capitalization	35.00%
Restricted net assets of subsidiaries	$ 5,100
Westar Energy Inc [Member]
Common Shareholders' Equity [Line Items]
Common stock - shares authorized (in shares)	1,000				275,000,000
Restriction on payment of dividends, minimum ratio of total capitalization	40.00%
KCPL [Member]
Common Shareholders' Equity [Line Items]
Common stock - shares authorized (in shares)	1,000				1,000
Restriction on payment of dividends, minimum ratio of total capitalization	40.00%
Retained earnings restrictions	$ 192
Evergy [Member]
Common Shareholders' Equity [Line Items]
Common stock - shares authorized (in shares)	600,000,000
Maximum [Member] | Westar Energy Inc [Member] | Master Credit Facility [Member]
Common Shareholders' Equity [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Maximum [Member] | KCPL [Member] | Master Credit Facility [Member]
Common Shareholders' Equity [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Maximum [Member] | Evergy [Member] | Master Credit Facility [Member]
Common Shareholders' Equity [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Maximum [Member] | Kcpl Greater Missouri Operations Member | Master Credit Facility [Member]
Common Shareholders' Equity [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%

Variable Interest Entities (Det

Variable Interest Entities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Property, plant and equipment	$ 18,782.5	$ 9,553.8
Current maturities of long-term debt	705.4	0
Accrued interest	110.9	72.7
Long-term debt, net	6,636.3	3,687.6
Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment	169.2	176.3
Current maturities of long-term debt	30.3	28.5
Accrued interest	0.5	0.7
Long-term debt, net	$ 51.1	81.4
Jeffrey Energy Center [Member]
Variable Interest Entity [Line Items]
VIE ownership percentage	8.00%
La Cygne Unit 2 [Member]
Variable Interest Entity [Line Items]
VIE ownership percentage	50.00%
Westar Energy Inc [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment	$ 9,718.3	9,553.8
Current maturities of long-term debt	300	0
Accrued interest	74.4	72.7
Long-term debt, net	3,389.8	3,687.6
Westar Energy Inc [Member] | Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment	169.2	176.3
Current maturities of long-term debt	30.3	28.5
Accrued interest	0.5	0.7
Long-term debt, net	$ 51.1	$ 81.4
Westar Energy Inc [Member] | Jeffrey Energy Center [Member]
Variable Interest Entity [Line Items]
VIE ownership percentage	8.00%
Westar Energy Inc [Member] | La Cygne Unit 2 [Member]
Variable Interest Entity [Line Items]
VIE ownership percentage	50.00%

Income Tax Expense (Details)

Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current income taxes
Federal	$ (67.4)	$ 0.1	$ (1)
State	2.2	0.4	0.3
Total	(65.2)	0.5	(0.7)
Deferred income taxes
Federal	160.1	122.8	155.2
State	(32.3)	30.7	32.9
Total	127.8	153.5	188.1
Investment Tax Credit
Amortization	(3.6)	(2.8)	(2.9)
Total	(3.6)	(2.8)	(2.9)
Income tax expense	$ 59	$ 151.2	$ 184.5
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax (in hundredths)	21.00%	35.00%	35.00%
COLI policies	(1.90%)	(3.10%)	(4.20%)
State income taxes	4.90%	4.10%	4.00%
Flow through depreciation for plant-related differences	0.80%	2.30%	3.10%
Federal tax credits	(6.40%)	(6.90%)	(1.80%)
Non-controlling interest	(0.40%)	(0.90%)	(0.90%)
AFUDC Equity	(0.10%)	(0.20%)	(0.80%)
Amortization of federal investment tax credits	(0.60%)	(0.60%)	(0.50%)
Changes In Uncertain Tax Positions, Net	0.10%	0.00%	0.00%
Federal or state tax rate change	(8.70%)	2.50%	0.00%
Valuation allowance	0.40%	0.30%	0.40%
Stock compensation	(0.40%)	(0.90%)	(0.50%)
Officer compensation limitation	1.20%	0.20%	0.00%
Other	(0.20%)	(0.80%)	0.00%
Effective income tax rate (in hundredths)	9.70%	31.00%	33.80%
KCPL [Member]
Current income taxes
Federal	$ 29.8	$ 37.4	$ 24.8
State	8.9	8.3	4.7
Total	38.7	45.7	29.5
Deferred income taxes
Federal	(3.4)	74.7	76.4
State	53	8.8	17
Total	49.6	83.5	93.4
Investment Tax Credit
Amortization	(1)	(1)	(1)
Total	(1)	(1)	(1)
Income tax expense	$ 87.3	$ 128.2	$ 121.9
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax (in hundredths)	21.00%	35.00%	35.00%
COLI policies	(0.20%)	(0.30%)	(0.20%)
State income taxes	5.50%	3.80%	4.10%
Flow through depreciation for plant-related differences	(2.50%)	0.50%	0.30%
Federal tax credits	(2.10%)	(2.40%)	(3.10%)
AFUDC Equity	(0.10%)	(0.70%)	(0.70%)
Amortization of federal investment tax credits	(0.40%)	(0.30%)	(0.30%)
Federal or state tax rate change	14.10%	5.30%	0.00%
Valuation allowance	0.00%	0.40%	0.00%
Stock compensation	(0.00%)	0.20%	(0.00%)
Officer compensation limitation	0.60%	0.10%	0.20%
Other	(1.00%)	0.00%	(0.10%)
Effective income tax rate (in hundredths)	34.90%	41.60%	35.20%
Westar Energy Inc [Member]
Current income taxes
Federal	$ (0.3)	$ 0.1	$ (1)
State	(1.8)	0.4	0.3
Total	(2.1)	0.5	(0.7)
Deferred income taxes
Federal	43.5	122.8	155.2
State	(42.9)	30.7	32.9
Total	0.6	153.5	188.1
Investment Tax Credit
Amortization	(2.8)	(2.8)	(2.9)
Total	(2.8)	(2.8)	(2.9)
Income tax expense	$ (4.3)	$ 151.2	$ 184.5
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax (in hundredths)	21.00%	35.00%	35.00%
COLI policies	(3.30%)	(3.10%)	(4.20%)
State income taxes	5.00%	4.10%	4.00%
Flow through depreciation for plant-related differences	1.60%	2.30%	3.10%
Federal tax credits	(10.40%)	(6.90%)	(1.80%)
Non-controlling interest	(0.60%)	(0.90%)	(0.90%)
AFUDC Equity	(0.20%)	(0.20%)	(0.80%)
Amortization of federal investment tax credits	(0.80%)	(0.60%)	(0.50%)
Changes In Uncertain Tax Positions, Net	0.10%	0.00%	0.00%
Federal or state tax rate change	(15.30%)	2.50%	0.00%
Valuation allowance	0.50%	0.30%	0.40%
Stock compensation	(0.80%)	(0.90%)	(0.50%)
Officer compensation limitation	1.80%	0.20%	0.00%
Other	0.20%	(0.80%)	0.00%
Effective income tax rate (in hundredths)	(1.20%)	31.00%	33.80%

Taxes Deferred Income Taxes (De

Taxes Deferred Income Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets, Gross [Abstract]
Tax credit carryforward	$ 508.1	$ 276.7
Income taxes refundable to customers, net	478.1	230.3
Deferred employee benefit costs	215.4	95.9
Net operating loss carryforward	383.3	70
Deferred state income taxes	62.5	63.8
Alternative minimum tax carryforward	73.4	52.2
Accrued liabilities	82.6	13.2
Other	193.5	97.9
Total deferred tax assets before valuation allowance	1,996.9	900
Valuation allowances	(27.3)	0
Total deferred tax assets, net	1,969.6	900
Deferred Tax Liabilities, Gross [Abstract]
Plant-related	(3,164.9)	(1,483.3)
Deferred employee benefit costs	(199.9)	(95.9)
Acquisition premium	(72.6)	(76.6)
Other	(131.4)	(59.9)
Total deferred tax liabilities	(3,568.8)	(1,715.7)
Net deferred income tax liabilities	(1,599.2)	(815.7)
Westar Energy Inc [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credit carryforward	307.1	276.7
Income taxes refundable to customers, net	233.1	230.3
Deferred employee benefit costs	89.6	95.9
Net operating loss carryforward	60.7	70
Deferred state income taxes	62.5	63.8
Alternative minimum tax carryforward	26.7	52.2
Accrued liabilities	13.6	13.2
Other	101.7	97.9
Total deferred tax assets before valuation allowance	895	900
Valuation allowances	(1.7)	0
Total deferred tax assets, net	893.3	900
Deferred Tax Liabilities, Gross [Abstract]
Plant-related	(1,491.6)	(1,483.3)
Deferred employee benefit costs	(89.6)	(95.9)
Acquisition premium	(72.6)	(76.6)
Other	(54.9)	(59.9)
Total deferred tax liabilities	(1,708.7)	(1,715.7)
Net deferred income tax liabilities	(815.4)	(815.7)
KCPL [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credit carryforward	194	185.8
Income taxes refundable to customers, net	186.9	179.1
Deferred employee benefit costs	118.3	124.6
Net operating loss carryforward	119.2	131.2
Deferred state income taxes	0	0
Alternative minimum tax carryforward	0	0
Accrued liabilities	32.8	26
Other	46.7	35.7
Total deferred tax assets before valuation allowance	697.9	682.4
Valuation allowances	0	0
Total deferred tax assets, net	697.9	682.4
Deferred Tax Liabilities, Gross [Abstract]
Plant-related	(1,199.7)	(1,127)
Deferred employee benefit costs	(86.1)	(96)
Acquisition premium	0	0
Other	(43.9)	(75.5)
Total deferred tax liabilities	(1,329.7)	(1,298.5)
Net deferred income tax liabilities	$ (631.8)	$ (616.1)

Taxes Net Operating Loss Carryf

Taxes Net Operating Loss Carryforwards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Valuation Allowance	$ 7.1
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	324.2	$ 38
Amount of Net Operating Losses related to business acquisition	78.1
Net operating losses year of origination [Abstract]
Net operating loss carryfowards originating in 2004	1.6
Net operating loss carryfowards originating in 2005	44.4
Net operating loss carryfowards originating in 2006	32
Net operating loss carryfowards originating in 2009	21.9
Net operating loss carryfowards originating in 2010	2.5
Net operating loss carryfowards originating in 2011	65.3
Net operating loss carryforwards originating in 2012	0.2
Net operating loss carryforwards originating in 2013	1.5
Net operating loss carryforwards originating in 2014	77.2
Net operating loss carryforwards originating in 2015	59.3
Net operating loss carryforwards originating in 2016	0.8
Net operating loss carryforwards originating in 2017	16.2
Net operating loss carryforwards originating in 2018	$ 1.3
Internal Revenue Service (IRS) [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2022
Internal Revenue Service (IRS) [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2037
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 59.1	26
Operating Loss Carryforwards, Valuation Allowance	$ 11.9
State and Local Jurisdiction [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2019
State and Local Jurisdiction [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2037
Westar Energy Inc [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 40.1	38
Net operating losses year of origination [Abstract]
Net operating loss carryfowards originating in 2004	0
Net operating loss carryfowards originating in 2005	0
Net operating loss carryfowards originating in 2006	0
Net operating loss carryfowards originating in 2009	0
Net operating loss carryfowards originating in 2010	0
Net operating loss carryfowards originating in 2011	0
Net operating loss carryforwards originating in 2012	0.2
Net operating loss carryforwards originating in 2013	0.8
Net operating loss carryforwards originating in 2014	25
Net operating loss carryforwards originating in 2015	0.2
Net operating loss carryforwards originating in 2016	0.4
Net operating loss carryforwards originating in 2017	12.3
Net operating loss carryforwards originating in 2018	1.2
Westar Energy Inc [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	20.6	26
KCPL [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	107.5	107.3
Net operating losses year of origination [Abstract]
Net operating loss carryfowards originating in 2004	0
Net operating loss carryfowards originating in 2005	0
Net operating loss carryfowards originating in 2006	0
Net operating loss carryfowards originating in 2009	0
Net operating loss carryfowards originating in 2010	0
Net operating loss carryfowards originating in 2011	38.4
Net operating loss carryforwards originating in 2012	0
Net operating loss carryforwards originating in 2013	0.3
Net operating loss carryforwards originating in 2014	12.3
Net operating loss carryforwards originating in 2015	55.6
Net operating loss carryforwards originating in 2016	0.3
Net operating loss carryforwards originating in 2017	0.6
Net operating loss carryforwards originating in 2018	0
KCPL [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 11.7	$ 23.9

Taxes Tax Credit Carryforwards

Taxes Tax Credit Carryforwards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	$ 333.8
Tax Credit Carryforwards Originating In 2000	7.3
Tax Credit Carryforwards Originating In 2001	9.8
Tax Credit Carryforwards Originating In 2002	0.3
Tax Credit Carryforwards Originating In 2003	0.3
Tax Credit Carryforwards Originating In 2004	0.3
Tax Credit Carryforwards Originating In 2005	0.3
Tax Credit Carryforwards Originating In 2006	0.3
Tax Credit Carryforwards Originating In 2007	0.6
Tax Credit Carryforwards Originating In 2008	39.8
Tax Credit Carryforwards Originating In 2009	47.7
Tax Credit Carryforwards Originating In 2010	18.3
Tax Credit Carryforwards Originating In 2011	13.3
Tax Credit Carryforwards Originating In 2012	13.7
Tax Credit Carryforwards Originating In 2013	23.5
Tax Credit Carryforwards Originating In 2014	23.6
Tax Credit Carryforwards Originating In 2015	23.5
Tax Credit Carryforwards Originating In 2016	26.1
Tax Credit Carryforwards Originating In 2017	43.3
Tax Credit Carryforwards Originating In 2018	41.8
Westar Energy Inc [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	134
Tax Credit Carryforwards Originating In 2000	7.3
Tax Credit Carryforwards Originating In 2001	9.7
Tax Credit Carryforwards Originating In 2002	0.2
Tax Credit Carryforwards Originating In 2003	0.2
Tax Credit Carryforwards Originating In 2004	0.2
Tax Credit Carryforwards Originating In 2005	0.2
Tax Credit Carryforwards Originating In 2006	0.2
Tax Credit Carryforwards Originating In 2007	0.5
Tax Credit Carryforwards Originating In 2008	0.5
Tax Credit Carryforwards Originating In 2009	0.2
Tax Credit Carryforwards Originating In 2010	0
Tax Credit Carryforwards Originating In 2011	0
Tax Credit Carryforwards Originating In 2012	2.9
Tax Credit Carryforwards Originating In 2013	10.5
Tax Credit Carryforwards Originating In 2014	10.2
Tax Credit Carryforwards Originating In 2015	10.1
Tax Credit Carryforwards Originating In 2016	10.1
Tax Credit Carryforwards Originating In 2017	34.5
Tax Credit Carryforwards Originating In 2018	36.5
KCPL [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	192.8
Tax Credit Carryforwards Originating In 2000	0
Tax Credit Carryforwards Originating In 2001	0
Tax Credit Carryforwards Originating In 2002	0
Tax Credit Carryforwards Originating In 2003	0
Tax Credit Carryforwards Originating In 2004	0
Tax Credit Carryforwards Originating In 2005	0
Tax Credit Carryforwards Originating In 2006	0
Tax Credit Carryforwards Originating In 2007	0
Tax Credit Carryforwards Originating In 2008	38.9
Tax Credit Carryforwards Originating In 2009	47.4
Tax Credit Carryforwards Originating In 2010	18.2
Tax Credit Carryforwards Originating In 2011	13.2
Tax Credit Carryforwards Originating In 2012	10.7
Tax Credit Carryforwards Originating In 2013	12.9
Tax Credit Carryforwards Originating In 2014	13
Tax Credit Carryforwards Originating In 2015	12.8
Tax Credit Carryforwards Originating In 2016	12.4
Tax Credit Carryforwards Originating In 2017	8.2
Tax Credit Carryforwards Originating In 2018	5.1
General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	333.8	$ 100
Amount of tax credit acquired in business combination	0.5
Tax Credit Carryforward, Valuation Allowance	0.4
General Business Tax Credit Carryforward [Member] | Westar Energy Inc [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	134	100
General Business Tax Credit Carryforward [Member] | KCPL [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	$ 192.8	184.6
General Business Tax Credit Carryforward [Member] | Minimum [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2020
General Business Tax Credit Carryforward [Member] | Maximum [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2038
Federal Alternative Minimum Tax Credit Carryforward [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	$ 73.4	52.2
Tax Credit Carryforward, Description	These credits do not expire and can be used to reduce taxes paid in the future or become refundable starting in 2018.
Tax Credit Carryforward, Valuation Allowance	$ 7.9
Federal Alternative Minimum Tax Credit Carryforward [Member] | Westar Energy Inc [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	26.7	52.2
State and Local Jurisdiction [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	$ 174.3	176.7
Tax Credit Carryforward, Description	The state income tax credits relate primarily to the Kansas high performance incentive program tax credits and expire in the years 2024 to 2033.
State and Local Jurisdiction [Member] | Westar Energy Inc [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	$ 173.1	176.7
State and Local Jurisdiction [Member] | KCPL [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	$ 1.2	$ 1.2

Taxes Valuation Allowance (Deta

Taxes Valuation Allowance (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Valuation Allowance [Line Items]
Valuation Allowance, Deferred Tax Asset, Change in Amount	$ 0.5
Valuation Allowance, Deferred Tax Asset, Explanation of Change	tax expense was recorded in continuing operations primarily related to AMT credits

Taxes Tax Reform (Details)

Taxes Tax Reform (Details) - USD ($) $ in Millions	Jun. 01, 2018	Dec. 31, 2018	Dec. 31, 2017
Regulatory liabilities		$ 2,218.8	$ 1,094
Westar Energy Inc [Member]
Regulatory liabilities		1,101.8	1,094
KCPL [Member]
Regulatory liabilities		$ 794.3	$ 770.9
Decrease in net deferred income tax liabilities due to tax reform	$ 46.6
Decrease in net deferred income tax liabilities for revaluation of deferred income tax assets and liabilities in rate base	28.8
Decrease in net deferred income tax liabilities for tax gross-up adjustment for ratemaking purposes due to tax reform	9.9
Income tax benefit from tax reform	$ 15.5

Quarterly Operating Results (_3

Quarterly Operating Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues	$ 1,199.8	$ 1,582.5	$ 893.4	$ 600.2	$ 594.8	$ 794.3	$ 609.3	$ 572.6	$ 4,275.9	$ 2,571	$ 2,562.1
Operating income	150.1	533.1	126.9	123.5	122.3	264.9	160.2	131.4	933.6	678.8	702.4
Net income (loss)	21.1	357.6	104.4	62.9	36.3	160.7	76	63.5	546	336.5	361.2
Net Income (Loss) Attributable to Parent	$ 18.5	$ 355	$ 101.8	$ 60.5	$ 33.8	$ 158.3	$ 72.1	$ 59.7	$ 535.8	$ 323.9	$ 346.6
Earnings Per Share, Basic and Diluted	$ 0.07	$ 1.32	$ 0.56	$ 0.42	$ 0.24	$ 1.11	$ 0.50	$ 0.42	$ 2.50	$ 2.27	$ 2.43
Basic EPS									2.50	2.27	2.43
Diluted EPS									$ 2.50	$ 2.27	$ 2.43
Westar Energy Inc [Member]
Revenues	$ 599	$ 764.8	$ 650.9	$ 600.2	$ 594.8	$ 794.3	$ 609.3	$ 572.6	$ 2,614.9	$ 2,571	$ 2,562.1
Operating income	94	256.9	76.1	123.5	122.3	264.9	160.2	131.4	550.5	678.8	702.4
Net income (loss)	30.6	178	77.6	62.9	36.3	160.7	76	63.5	349.1	336.5	361.2
Net Income (Loss) Attributable to Parent	28	175.4	75	60.5	33.8	158.3	72.1	59.7	338.9	323.9	346.6
KCPL [Member]
Revenues	414.2	559.6	452.2	397.1	416.4	595.7	482.7	395.9	1,823.1	1,890.7	1,875.4
Operating income	44.7	189.4	114.7	61	75.4	219.8	126.2	65	409.8	486.4	519.3
Net income (loss)	$ (2.2)	$ 120.3	$ 24.6	$ 20.2	$ 1.9	$ 114.1	$ 49.6	$ 14.2	162.9	179.8	225
Net Income (Loss) Attributable to Parent									$ 162.9	$ 179.8	$ 225

Schedule I Financial Statements

Schedule I Financial Statements of Parent Company Statements of Income & OCI (Details) - USD ($) $ in Millions	3 Months Ended								7 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
OPERATING EXPENSES:
Operating and maintenance										$ 1,115.8	$ 563.5	$ 587.2
Total operating expenses										3,342.3	1,892.2	1,859.7
INCOME FROM OPERATIONS	$ 150.1	$ 533.1	$ 126.9	$ 123.5	$ 122.3	$ 264.9	$ 160.2	$ 131.4		933.6	678.8	702.4
OTHER INCOME (EXPENSE):
Equity in earnings from subsidiaries										5.4	6.7	6.5
Investment earnings										8.8	4	2.5
Other expense										(78.7)	(39.1)	(38.6)
Total other income (expense), net										(54.4)	(26.8)	(1.5)
Interest expense										279.6	171	161.7
INCOME BEFORE INCOME TAXES										599.6	481	539.2
Income tax (expense) benefit										(59)	(151.2)	(184.5)
Net income (loss)	21.1	357.6	104.4	62.9	36.3	160.7	76	63.5		546	336.5	361.2
COMPREHENSIVE INCOME
Net income (loss)	$ 21.1	$ 357.6	$ 104.4	$ 62.9	$ 36.3	$ 160.7	$ 76	$ 63.5		546	336.5	361.2
OTHER COMPREHENSIVE INCOME:
Gain (loss) on derivative hedging instruments										(5.4)	0	0
Income tax benefit										(1.4)	0	0
Net gain (loss) on derivative hedging instruments										(4)	0	0
Derivative hedging activity, net of tax										(4)	0	0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest										543	336.5	361.2
Total other comprehensive income										(3)	0	0
Comprehensive income										$ 532.8	$ 323.9	$ 346.6
Evergy [Member]
OPERATING EXPENSES:
Operating and maintenance									$ 54.6
Total operating expenses									54.6
INCOME FROM OPERATIONS									(54.6)
OTHER INCOME (EXPENSE):
Equity in earnings from subsidiaries									364.7
Investment earnings									26.3
Other expense									(2.6)
Total other income (expense), net									388.4
Interest expense									19.6
INCOME BEFORE INCOME TAXES									314.2
Income tax (expense) benefit									(10.7)
Net income (loss)									324.9
COMPREHENSIVE INCOME
Net income (loss)									324.9
OTHER COMPREHENSIVE INCOME:
Gain (loss) on derivative hedging instruments									(5.4)
Income tax benefit									1.4
Net gain (loss) on derivative hedging instruments									(4)
Derivative hedging activity, net of tax									(4)
Other comprehensive income from subsidiaries, net of tax									1
Total other comprehensive income									(3)
Comprehensive income									$ 321.9

Schedule I Financial Statemen_2

Schedule I Financial Statements of Parent Company Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jun. 04, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 160.3		$ 3.4
Income taxes receivable	68		0
Prepaid expenses and other assets	79.1		39.8
Total Current Assets	1,681		727
OTHER ASSETS:
Other	396.5		244.8
Total Other Assets	4,965.4		1,167.3
Total Assets	25,598.1		11,624.4
CURRENT LIABILITIES:
Accrued interest	110.9		72.7
Accrued taxes	133.6		87.7
Other	171.9		64.4
Total Current Liabilities	2,867.2		823.7
LONG-TERM LIABILITIES:
Long-term debt, net	6,636.3		3,687.6
Other	236.7		133.3
Total Long-Term Liabilities	12,740.2		6,940.3
EQUITY
Common stock	8,685.2		2,734.8
Retained earnings	1,346		1,173.3
Accumulated other comprehensive loss	(3)		0
Total shareholders' equity	10,028.2		3,908.1
Commitments and Contingencies
TOTAL LIABILITIES AND EQUITY	25,598.1		$ 11,624.4
Evergy [Member]
CURRENT ASSETS:
Cash and cash equivalents	107.1	$ 0
Accounts receivable from subsidiaries	35.2
Notes receivable from subsidiaries	2
Prepaid expenses and other assets	2.2
Total Current Assets	146.5
OTHER ASSETS:
Investment in subsidiaries	9,785.6
Notes receivable from subsidiaries	634.9
Deferred income taxes	36.3
Other	1.1
Total Other Assets	10,457.9
Total Assets	10,604.4
CURRENT LIABILITIES:
Accounts payable to subsidiaries	28.1
Accrued interest	2.1
Derivative instruments	5.4
Other	6.3
Total Current Liabilities	41.9
LONG-TERM LIABILITIES:
Long-term debt, net	638.1
Other	17.6
Total Long-Term Liabilities	655.7
EQUITY
Common stock	8,668.3
Retained earnings	1,241.5
Accumulated other comprehensive loss	(3)
Total shareholders' equity	9,906.8
TOTAL LIABILITIES AND EQUITY	$ 10,604.4

Schedule I Financial Statemen_3

Schedule I Financial Statements of Parent Company Balance Sheet Parenthetical (Details) - shares	Dec. 31, 2018	Dec. 31, 2017
Common Stock, Shares Authorized	600,000,000	275,000,000
Common Stock, Shares, Issued	255,326,252	142,094,275
Evergy [Member]
Common Stock, Shares Authorized	600,000,000
Common Stock, Shares, Issued	255,326,252

Schedule I Financial Statemen_4

Schedule I Financial Statements of Parent Company Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								7 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income (loss)	$ 21.1	$ 357.6	$ 104.4	$ 62.9	$ 36.3	$ 160.7	$ 76	$ 63.5		$ 546	$ 336.5	$ 361.2
Adjustments to reconcile income to net cash from operating activities:
Non-cash compensation										29.9	8.8	9.3
Net deferred income taxes and credits										124.2	149.6	185.2
Equity in earnings from subsidiaries										(5.4)	(6.7)	(6.5)
Changes in working capital items:
Prepaid expenses and other current assets										(128.1)	55.8	(18.3)
Accrued taxes										(76.4)	9.2	(5.9)
Other current liabilities										92	(118)	(86.4)
Changes in other assets										66.8	32	21.4
Changes in other liabilities										(15.9)	19.3	23.3
Net Cash Provided by (Used in) Operating Activities										1,497.8	912.7	803.8
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Cash acquired from the merger with Great Plains Energy										1,154.2	0	0
Proceeds from settlement of interest rate swap										140.6	0	0
Other investing activities										(17.6)	(3.6)	(4.1)
Net Cash Provided by (Used in) Investing Activities										197.4	(780.8)	(994.1)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Proceeds from long-term debt										290.9	296.2	396.3
Retirements of long-term debt										(395.8)	(125)	(50)
Short term debt, net										(104)	(91.3)	116.2
Cash dividends paid										(475)	(223.1)	(204.3)
Repurchase of common stock										(1,042.3)	0	0
Other financing activities										(21.3)	(15.7)	(8.1)
Net cash from financing activities										(1,538.4)	(131.6)	$ 190.2
Cash and Cash Equivalents at Beginning of Year				$ 3.4						3.4
Cash and Cash Equivalents at End of Period	160.3				$ 3.4				$ 160.3	160.3	$ 3.4
Evergy [Member]
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income (loss)									324.9
Adjustments to reconcile income to net cash from operating activities:
Non-cash compensation									10
Net deferred income taxes and credits									(6.3)
Equity in earnings from subsidiaries									(364.7)
Changes in working capital items:
Accounts receivable from subsidiaries									(8.5)
Prepaid expenses and other current assets									(1.2)
Accounts payable to subsidiaries									4.7
Accrued taxes									(35.2)
Other current liabilities									(11.2)
Cash dividends from subsidiaries									236
Changes in other assets									0.1
Changes in other liabilities									20
Net Cash Provided by (Used in) Operating Activities									168.6
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Cash acquired from the merger with Great Plains Energy									1,142.2
Proceeds from settlement of interest rate swap									140.6
Net Cash Provided by (Used in) Investing Activities									1,282.8
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Short term debt, net									(56.1)
Cash dividends paid									(245.9)
Repurchase of common stock									(1,042.3)
Net cash from financing activities									(1,344.3)
Net Change in Cash and Cash Equivalents									107.1
Cash and Cash Equivalents at End of Period	$ 107.1								$ 107.1	$ 107.1

Schedule II Valuation and Quali

Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 6.7	$ 6.7	$ 5.3
Additions charged to costs and expenses	20.7	10.5	12.2
Additions charged to other accounts	16.9	7	6.2
Deductions	35.1	17.5	17
Balance at end of period	9.2	6.7	6.7
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | Westar Energy Inc [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	6.7	6.7	5.3
Additions charged to costs and expenses	9	10.5	12.2
Additions charged to other accounts	7.4	7	6.2
Deductions	19.2	17.5	17
Balance at end of period	3.9	6.7	6.7
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | KCPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	2.2	1.8	1.8
Additions charged to costs and expenses	13.1	7.5	6.4
Additions charged to other accounts	4.4	5.6	5.5
Deductions	15.9	12.7	11.9
Balance at end of period	3.8	2.2	1.8
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	0
Additions charged to costs and expenses	2.2
Additions charged to other accounts	26.8
Deductions	1.7
Balance at end of period	27.3	0
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] | Westar Energy Inc [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	0
Additions charged to costs and expenses	1.7
Additions charged to other accounts	0
Deductions	0
Balance at end of period	1.7	0
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] | KCPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 0	0	0.7
Additions charged to costs and expenses		1.2	0
Additions charged to other accounts		0	0
Deductions		1.2	0.7
Balance at end of period		$ 0	$ 0