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Significant Accounting Policies (Details) | 12 Months Ended
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Dec. 31, 2017
Significant Accounting Policies [Abstract] |
Percentage of tuition revenue in total revenue | 96.00%
Unused books and academic material refundable period | 21 days

X
- Definition Percentage of tuition revenue in total revenue. + References No definition available. + Details
Name: | stra_PercentageOfTuitionRevenueInRevenue
Namespace Prefix: | stra_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The period to return unused books and related academic materials in order to receive a full refund. + References No definition available. + Details
Name: | stra_UnusedBooksAndAcademicMaterialRefundablePeriod
Namespace Prefix: | stra_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration