Represents the fixed charge coverage ratio as of the balance sheet date.

No definition available.

Name:	cor_DebtInstrumentFixedChargeCoverageRatio
Namespace Prefix:	cor_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the leverage ratio as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	cor_DebtInstrumentLeverageRatio
Namespace Prefix:	cor_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the secured debt ratio as of the balance sheet date.

+ References

No definition available.

+ Details

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Namespace Prefix:	cor_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the secured debt ratio defined as consolidated total secured debt to total gross asset value as per the financial covenant.

+ References

No definition available.

+ Details

Name:	cor_DebtInstrumentSecuredRatioCovenantCompliance
Namespace Prefix:	cor_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
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

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

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

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

- 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

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

Carrying value as of the balance sheet date of uncollateralized debt obligation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

+ References

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

+ Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
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Data Type:	na
Balance Type:
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- Details

Name:	srt_RangeAxis=srt_MaximumMember
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Balance Type:
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Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cor_CreditAgreementMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cor_SeniorUnsecuredTermLoan2022Member
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=cor_SeniorUnsecuredTermLoanMember
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Data Type:	na
Balance Type:
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Name:	us-gaap_DebtInstrumentAxis=cor_SeniorUnsecuredTermLoan2024Member
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- Details

Name:	us-gaap_DebtInstrumentAxis=cor_SeniorUnsecuredTermLoan2025Member
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Balance Type:
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- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_PartnershipInterestMember
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Debt - Revolving Credit Facility (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Nov. 08, 2019
Debt
Total principal outstanding	$ 1,624,000	$ 1,487,500
Revolving Credit Facility
Debt
Total principal outstanding	$ 99,000	62,500
Revolving Credit Facility \| LIBOR \| Minimum
Debt
Interest rate margin (as a percent)	125.00%
Debt Instrument, Basis Spread on Variable Rate	125.00%
Revolving Credit Facility \| LIBOR \| Maximum
Debt
Interest rate margin (as a percent)	185.00%
Debt Instrument, Basis Spread on Variable Rate	185.00%
Revolving Credit Facility \| Base Rate \| Minimum
Debt
Interest rate margin (as a percent)	25.00%
Debt Instrument, Basis Spread on Variable Rate	25.00%
Revolving Credit Facility \| Base Rate \| Maximum
Debt
Interest rate margin (as a percent)	85.00%
Debt Instrument, Basis Spread on Variable Rate	85.00%
Credit Agreement
Debt
Leverage ratio (as a percent)	31.10%
Secured debt ratio, Covenant (as a percent)	0.00%
Fixed charge coverage ratio	6.5
Credit Agreement \| Minimum
Debt
Fixed charge coverage ratio	1.5
Credit Agreement \| Maximum
Debt
Leverage ratio (as a percent)	0.60%
Secured debt ratio (as a percent)	0.40%
Credit Agreement \| Revolving Credit Facility \| LIBOR
Debt
Interest rate margin (as a percent)	125.00%
Debt Instrument, Basis Spread on Variable Rate	125.00%
2022 Senior Unsecured Term Loan \| Senior Unsecured Term Loan
Debt
Total principal outstanding	$ 200,000	200,000
2024 Senior Unsecured Term Loan \| Senior Unsecured Term Loan
Debt
Unsecured term loan			$ 150,000
2025 Senior Unsecured Term Loan
Debt
Interest rate margin (as a percent)	120.00%
Leverage ratio (as a percent)	31.10%
Debt Instrument, Basis Spread on Variable Rate	120.00%
2025 Senior Unsecured Term Loan \| Senior Unsecured Term Loan
Debt
Total principal outstanding	$ 350,000	$ 350,000
2025 Senior Unsecured Term Loan \| Senior Unsecured Term Loan \| Base Rate \| Minimum
Debt
Interest rate margin (as a percent)	20.00%
Debt Instrument, Basis Spread on Variable Rate	20.00%
Operating partnership \| Revolving Credit Facility
Debt
Maximum borrowing capacity			450,000
Operating partnership \| Credit Agreement
Debt
Borrowing capacity at end of period	$ 450,000
Letters of credit outstanding	6,100
Amount available for borrowing under the facility	$ 344,900
Operating partnership \| 2025 Senior Unsecured Term Loan \| LIBOR \| Minimum
Debt
Interest rate margin (as a percent)	120.00%
Debt Instrument, Basis Spread on Variable Rate	120.00%
Operating partnership \| 2025 Senior Unsecured Term Loan \| Revolving Credit Facility \| LIBOR \| Maximum
Debt
Interest rate margin (as a percent)	180.00%
Debt Instrument, Basis Spread on Variable Rate	180.00%
Operating partnership \| 2025 Senior Unsecured Term Loan \| Senior Unsecured Term Loan
Debt
Unsecured term loan			$ 350,000