Notes and Other Debt - Schedule of Notes and Other Debt (Parenthetical) (Details)	8 Months Ended	9 Months Ended
Dec. 31, 2015	Sep. 30, 2016
Senior Secured Notes - 6.00% Due April 15, 2023
Debt Instrument [Line Items]
Issuance senior notes, stated percentage	6.00%	6.00%
Debt instrument, maturity date	Apr. 15, 2023	Apr. 15, 2023
Debt instrument, imputed interest rate	6.29%	6.29%
Senior Unsecured Notes - 8.25% Due October 15, 2023
Debt Instrument [Line Items]
Issuance senior notes, stated percentage	8.25%	8.25%
Debt instrument, maturity date	Oct. 15, 2023	Oct. 15, 2023
Debt instrument, imputed interest rate	9.06%	9.06%
Senior Secured Term Loan B Facility
Debt Instrument [Line Items]
Debt instrument, maturity date	Oct. 24, 2022	Oct. 24, 2022
Debt instrument, imputed interest rate	5.66%	5.66%
Senior Secured Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, expiration date		Apr. 24, 2020

Debt instrument imputed interest rate.

No definition available.

Name:	csal_DebtInstrumentImputedInterestRate
Namespace Prefix:	csal_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=csal_SixPercentageSeniorSecuredNotesDueAprilFifteenTwoThousandTwentyThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=csal_EightPointTwoFivePercentageSeniorUnsecuredNotesDueOctoberFifteenTwoThousandTwentyThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=csal_SeniorSecuredTermLoanBFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=csal_SeniorSecuredRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: