Summary of Significant Accounting Policies - Share-based Compensation (Details)	12 Months Ended
Dec. 31, 2019
Accounting Policies [Abstract]
Forfeiture rate since inception of plans	5.00%

Share-based Compensation Arrangement by Share-based Payment Award, Forfeiture Rate Since Inception of Plans

No definition available.

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Namespace Prefix:	core_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration