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Significant Accounting Policies (Details) $ in Thousands | 9 Months Ended
--- | ---
Sep. 30, 2017 USD ($)
Significant Accounting Policies [Abstract] |
Items within other comprehensive income | $ 0
Percentage of tuition revenue in total revenue | 96.00%
Unused books and academic material refundable period | 21 days

X
- Definition Represents activity within other comprehensive income. + References No definition available. + Details
Name: | stra_ItemsWithinOtherComprehensiveIncome
Namespace Prefix: | stra_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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