Assets and Liabilities, at Fair Value - Suriwongse Bonds (Details) $ in Millions	Sep. 30, 2016 USD ($)
Corporate Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial Instruments, Owned, Corporate Debt, at Fair Value	$ 3.0

Fair value of firm holdings in corporate fixed income securities. Includes pledged and unpledged holdings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969

Name:	us-gaap_FinancialInstrumentsOwnedCorporateDebtAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant