Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Assets at Fair Value
Financial instruments owned	$ 664	$ 1,096,181
Investments	18,889	20,478
Liabilities at Fair Value
Securities sold but not yet purchased		132,730
Level 1
Assets at Fair Value
Total		5,342
Liabilities at Fair Value
Total financial liabilities at fair value		130,210
Level 1 | Preferred stock
Assets at Fair Value
Financial instruments owned		2,439
Level 1 | U.S. Government obligations
Assets at Fair Value
Financial instruments owned		1,996
Liabilities at Fair Value
Securities sold but not yet purchased		128,504
Level 1 | Equity securities
Assets at Fair Value
Financial instruments owned		675
Liabilities at Fair Value
Securities sold but not yet purchased		2
Level 1 | Derivatives
Assets at Fair Value
Financial instruments owned		232
Liabilities at Fair Value
Securities sold but not yet purchased		1,704
Level 2
Assets at Fair Value
Total		1,087,899
Liabilities at Fair Value
Total financial liabilities at fair value		2,520
Level 2 | Agency mortgage-backed securities
Assets at Fair Value
Financial instruments owned		903,928
Level 2 | Loans
Assets at Fair Value
Financial instruments owned		77,573
Level 2 | Federal agency obligations
Assets at Fair Value
Financial instruments owned		46,021
Level 2 | Corporate debt securities
Assets at Fair Value
Financial instruments owned		30,246
Liabilities at Fair Value
Securities sold but not yet purchased		2,520
Level 2 | Residential mortgage-backed securities
Assets at Fair Value
Financial instruments owned		23,077
Level 2 | Commercial mortgage-backed securities
Assets at Fair Value
Financial instruments owned		4,880
Level 2 | U.S. Government obligations
Assets at Fair Value
Financial instruments owned		100
Level 2 | Other debt obligations
Assets at Fair Value
Financial instruments owned		2,074
Level 3
Assets at Fair Value
Total		23,418
Level 3 | Agency mortgage-backed securities
Assets at Fair Value
Financial instruments owned		1,110
Level 3 | Residential mortgage-backed securities
Assets at Fair Value
Financial instruments owned		149
Level 3 | Commercial mortgage-backed securities
Assets at Fair Value
Financial instruments owned		18
Level 3 | Equity securities
Assets at Fair Value
Financial instruments owned		28
Level 3 | Collateralized debt obligations
Assets at Fair Value
Financial instruments owned		671
Level 3 | Derivatives
Assets at Fair Value
Financial instruments owned		964
Level 3 | Investments
Assets at Fair Value
Investments	18,900	20,478
Total
Assets at Fair Value
Total		1,116,659
Liabilities at Fair Value
Total financial liabilities at fair value		132,730
Total | Agency mortgage-backed securities
Assets at Fair Value
Financial instruments owned		905,038
Total | Loans
Assets at Fair Value
Financial instruments owned		77,573
Total | Federal agency obligations
Assets at Fair Value
Financial instruments owned		46,021
Total | Corporate debt securities
Assets at Fair Value
Financial instruments owned		30,246
Liabilities at Fair Value
Securities sold but not yet purchased		2,520
Total | Residential mortgage-backed securities
Assets at Fair Value
Financial instruments owned		23,226
Total | Commercial mortgage-backed securities
Assets at Fair Value
Financial instruments owned		4,898
Total | Preferred stock
Assets at Fair Value
Financial instruments owned		2,439
Total | U.S. Government obligations
Assets at Fair Value
Financial instruments owned		2,096
Liabilities at Fair Value
Securities sold but not yet purchased		128,504
Total | Other debt obligations
Assets at Fair Value
Financial instruments owned		2,074
Total | Equity securities
Assets at Fair Value
Financial instruments owned		703
Liabilities at Fair Value
Securities sold but not yet purchased		2
Total | Collateralized debt obligations
Assets at Fair Value
Financial instruments owned		671
Total | Derivatives
Assets at Fair Value
Financial instruments owned		1,196
Liabilities at Fair Value
Securities sold but not yet purchased		1,704
Total | Investments
Assets at Fair Value
Investments		$ 20,478