Fair Value Measurements - Assets and Liabilities Not Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014
Financial Instruments Not Measured at Fair Value on Recurring Basis [Line items]
Securities purchased under agreements to resell	$ 206,499		$ 251,606
Level 1
Financial Instruments Not Measured at Fair Value on Recurring Basis [Line items]
Cash	50,364		32,632
Cash segregated for regulatory and other purposes			18,594
Deposits with clearing organization	18,034		12,322
Securities purchased under agreements to resell			1,606
Drafts payable	48,011		35,373
Level 2
Financial Instruments Not Measured at Fair Value on Recurring Basis [Line items]
Securities borrowed	224,672		242,172
Receivables from brokers	49,458		38,149
Securities failed to deliver	7,799		11,055
Clearing organizations	25,030		21,106
Other	53,954		1,993
Total Receivable from brokers, dealers and clearing organizations	360,913		314,475
Receivable from customers	840,355		864,189
Investments	53,286	[1]	51,246	[2]
Bank call loans	100,200		59,400
Securities loaned	130,658		137,892
Payable to brokers	3,316		4,559
Securities failed to receive	21,513		23,573
Other	9,059		91,137
Total payables to brokers, dealers and clearing organizations	164,546		257,161
Payables to customers	594,833		652,256
Securities sold under agreements to repurchase	651,445		687,440
Warehouse payable	54,341		16,683
Senior secured notes	154,568		157,782
Level 3
Financial Instruments Not Measured at Fair Value on Recurring Basis [Line items]
Mortgage servicing rights	41,838		42,279
Carrying Value
Financial Instruments Not Measured at Fair Value on Recurring Basis [Line items]
Cash	50,364		32,632
Cash segregated for regulatory and other purposes			18,594
Deposits with clearing organization	18,034		12,322
Securities borrowed	224,672		242,172
Receivables from brokers	49,458		38,149
Securities failed to deliver	7,799		11,055
Clearing organizations	25,030		21,106
Other	53,954		1,993
Total Receivable from brokers, dealers and clearing organizations	360,913		314,475
Receivable from customers	840,355		864,189
Securities purchased under agreements to resell			1,606
Mortgage servicing rights	28,168		30,140
Investments	53,286	[1]	51,246	[2]
Drafts payable	48,011		35,373
Bank call loans	100,200		59,400
Securities loaned	130,658		137,892
Payable to brokers	3,316		4,559
Securities failed to receive	21,513		23,573
Other	9,059		91,137
Total payables to brokers, dealers and clearing organizations	164,546		257,161
Payables to customers	594,833		652,256
Securities sold under agreements to repurchase	651,445		687,440
Warehouse payable	54,341		16,683
Senior secured notes	150,000		150,000
Estimate of Fair Value Measurement
Financial Instruments Not Measured at Fair Value on Recurring Basis [Line items]
Cash	50,364		32,632
Cash segregated for regulatory and other purposes			18,594
Deposits with clearing organization	18,034		12,322
Securities borrowed	224,672		242,172
Receivables from brokers	49,458		38,149
Securities failed to deliver	7,799		11,055
Clearing organizations	25,030		21,106
Other	53,954		1,993
Total Receivable from brokers, dealers and clearing organizations	360,913		314,475
Receivable from customers	840,355		864,189
Securities purchased under agreements to resell			1,606
Mortgage servicing rights	41,838		42,279
Investments	53,286	[1]	51,246	[2]
Drafts payable	48,011		35,373
Bank call loans	100,200		59,400
Securities loaned	130,658		137,892
Payable to brokers	3,316		4,559
Securities failed to receive	21,513		23,573
Other	9,059		91,137
Total payables to brokers, dealers and clearing organizations	164,546		257,161
Payables to customers	594,833		652,256
Securities sold under agreements to repurchase	651,445		687,440
Warehouse payable	54,341		16,683
Senior secured notes	$ 154,568		$ 157,782

[1] Included in other assets on the consolidated balance sheet.

[2] Included in other assets on the consolidated balance sheet.