Debt Instrument, Periodic Payment, Percent

No definition available.

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum increase in the available borrowing capacity of the credit facility subject to certain limitations and satisfaction of certain conditions, including compliance with certain financial covenants.

+ References

No definition available.

+ Details

Name:	knl_LineOfCreditFacilityBorrowingCapacityAvailableIncrease
Namespace Prefix:	knl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Facility, Borrowing Capacity Available Increase, Percent Of EBITDA

+ References

No definition available.

+ Details

Name:	knl_LineOfCreditFacilityBorrowingCapacityAvailableIncreasePercentOfEBITDA
Namespace Prefix:	knl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of amortization expense attributable to debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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-Name Accounting Standards Codification
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-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(8))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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-Name Accounting Standards Codification
-Topic 835
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments including both interest and principal payments.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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-Paragraph 1
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt issuance costs related to line of credit arrangements. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

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-Publisher FASB
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+ Details

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Balance Type:	credit
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=knl_AmendedCreditAgreementMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=knl_TermLoanMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=knl_MulticurrencyTermLoanMember
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Balance Type:
Period Type:

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
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- Details

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INDEBTEDNESS - Narrative (Details)		3 Months Ended		12 Months Ended
INDEBTEDNESS - Narrative (Details)	Aug. 26, 2019	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 EUR (€)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 23, 2018 USD ($)	Jan. 23, 2018 EUR (€)
Debt Instrument [Line Items]
Pre-payments of term loans				$ 65,900,000		$ 17,100,000	$ 177,900,000
Borrowings under revolving credit facility				$ 414,500,000		$ 417,500,000	490,500,000
Commitment fee rate						0.225%
Quarterly payments, percent of annum				5.00%	5.00%
Debt maturity				5 years	5 years
Amortization expense related to the deferred financing fees				$ 900,000		$ 1,000,000.0	1,100,000
Loss on extinguishment of debt						400,000	$ 1,400,000
Credit Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Commitments				$ 400,000,000.0		$ 400,000,000.0
Amended Credit Agreement
Debt Instrument [Line Items]
Commitments								$ 750,000,000.0
Borrowing capacity available increase								$ 250,000,000.0
Available increase, percent of EBITDA								90.00%	90.00%
Amended Credit Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Commitments								$ 400,000,000.0
Amended Credit Agreement \| U.S. term loan
Debt Instrument [Line Items]
Debt face amount								$ 250,000,000.0
Amended Credit Agreement \| Multi-currency term loans
Debt Instrument [Line Items]
Debt face amount \| €									€ 81,700,000
Credit Agreement \| Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	0.50%
Credit Agreement \| Eurocurrency Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.00%
Credit Agreement \| Revolving Credit Facility \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)							5.25%
Borrowings under revolving credit facility							$ 10,000,000.0
Credit Agreement \| Revolving Credit Facility \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				1.65%	1.65%		3.27%
Borrowings under revolving credit facility				$ 61,000,000.0			$ 128,500,000
Credit Agreement \| Letter of Credit
Debt Instrument [Line Items]
Weighted average interest rate						1.50%
Amended Credit Agreement
Debt Instrument [Line Items]
Debt issuance costs, line of credit			$ 300,000
Loss on extinguishment of debt			$ 200,000
Amended Credit Agreement \| U.S. term loan
Debt Instrument [Line Items]
Pre-payments of term loans		$ 50,000,000.0
Interest rate incurred				1.65%			3.30%
Debt fixed quarterly payments				$ 2,800,000
Amended Credit Agreement \| Multi-currency term loans
Debt Instrument [Line Items]
Interest rate incurred				1.50%			1.50%
Debt fixed quarterly payments \| €					€ 700,000