Note 3 - Certificates of Deposit (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Certificates Of Deposit Maximum Value Per Deposit	$ 250,000
Certificates of Deposit, at Carrying Value, Current and Noncurrent	3,874,000		$ 4,095,000
Payments to Acquire Investments, Total	1,458
Certificates of Deposit [Member]
Payments to Acquire Investments, Total	489,000	965,000
Proceeds from Sale, Maturity and Collection of Investments, Total	$ 710,000	$ 980,000

The carrying value of current and noncurrent assets classified as certificates of deposit.

No definition available.

Name:	ckx_CertificatesOfDepositAtCarryingValueCurrentAndNoncurrent
Namespace Prefix:	ckx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents for the amount of certificates of deposit greater than three months

+ References

No definition available.

+ Details

Name:	ckx_CertificatesOfDepositMaximumValuePerDeposit
Namespace Prefix:	ckx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

+ Details

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

- Definition

The cash inflow associated with the sale, maturity and collection of all investments such as debt, security and so forth during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

+ Details

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

- Details

Name:	invest_InvestmentAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: