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Capital Loss Carryforward 3 [Member] Capital Loss Carryforwards Expiring 2016 or Later [Member] Carrying Reported Amount Fair Value Disclosure [Member] Carrying Amount [Member] Cash And Cash Equivalents [Abstract] Cash and Cash Equivalents [Abstract] Cash And Cash Equivalents And Restricted Cash At Carrying Value Cash And Cash Equivalents And Restricted Cash At Carrying Value Total Cash And Cash Equivalents At Carrying Value Cash and cash equivalents at end of period Cash and cash equivalents at beginning of period Cash and cash equivalents Cash And Cash Equivalents Disclosure [Text Block] Cash and Cash Equivalents, Including Restricted Cash Cash And Cash Equivalents Fair Value Disclosure Cash and cash equivalents Cash And Cash Equivalents [Line Items] Cash and Cash Equivalents [Line Items] Cash And Cash Equivalents [Member] Cash or Cash Equivalents [Member] Cash And Cash Equivalents Period Increase Decrease Net increase in cash and cash equivalents Cash And Cash Equivalents Policy [Text Block] Cash and Cash Equivalents Cash And Cash Equivalents Restricted Cash And Cash Equivalents Policy Restricted Cash Cash Dividends Paid To Parent Company By 50 Percent Or Less Owned Persons Distribution to Blackstone Mortgage Trust, Inc. 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Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest Comprehensive income attributable to non-controlling interests Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest Comprehensive income The percentage per annum multiplied by outstanding Equity balance in computation of management fees. Computed Management Fee Percent Of Outstanding Equity Balance Management fee - percent of outstanding Equity balance Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Concentration Risk By Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Percentage 1 Percentage of revenue generated from international source Condominium Property [Member] Condominium Property [Member] Condominium [Member] Consolidated Entities [Member] Consolidation Variable Interest Entities [Member] Consolidation Policy [Text Block] Principles of Consolidation Contractual Payment [Member] Contractual Payment [Member] Contractual Payments [Member] Conversion Of Stock Description Description of convertible notes conversion Convertible Debt Fair Value Disclosures Convertible notes, net Convertible Notes Payable Convertible notes, net Convertible Notes Payable [Member] Convertible Senior Notes [Member] Convertible Notes Policy [Text Block] Convertible Notes Policy [Text 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