Investments - Financial Instrument Obligations (Details) (Financial instrument liabilities, USD $) In Thousands, unless otherwise specified	Sep. 30, 2014
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	$ 19,512
Estimated Fair Value	20,264
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	655
Estimated Fair Value	532
Market indices
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	18,685
Estimated Fair Value	19,603
Covered call options
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	80
Estimated Fair Value	123
Naked put options
Schedule of Available-for-sale Securities [Line Items]
Initial Obligation	92
Estimated Fair Value	$ 6