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compensation Shares Granted, Value, Share-Based Payment Arrangement, before Forfeiture Class B Common Stock, Class B-1 [Member] Class B Common Stock, Class B1 [member] Class B Common Stock, Class B1 [Member] Long-term restricted cash Restricted Cash and Cash Equivalents, Noncurrent Document Transition Report Document Transition Report Document Quarterly Report Document Quarterly Report Lessee, Operating Lease, Renewal Term Operating Lease Renewal Term Operating Lease Renewal Term Investments in privately-held equity investments Payments to Acquire Other Investments Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Current Reporting Status Entity Current Reporting Status Retained Earnings [Member] Retained Earnings [Member] Contingent liability to SGX, amount of irrevocable letters of credit Guarantee Collateral Guarantee Collateral Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Income tax benefit (expense) OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Change in performance bond and guaranty fund contributions Change in performance bond and guaranty fund contributions Change in performance bond and guaranty fund contributions Entity Filer Category Entity Filer Category Nonrecurring fair value [Abstract] Nonrecurring fair value [Abstract] Nonrecurring fair value [Abstract] Income Statement Location [Domain] Statement of Income Location, Balance [Domain] Purchases of available-for-sale marketable securities Payments to Acquire Debt Securities, Available-for-Sale