Information of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Assets:
Marketable Securities	$ 568,279		$ 567,302
Derivative assets	732		1,305
Total assets	569,011		568,607
Liabilities:
Junior subordinated notes, at fair value	13,048		11,911
CDO notes payable, at fair value	431,142		377,235
Derivative liabilities	81,998		113,331
Warrants and investor SARs	29,731		31,304
Total liabilities	555,919		533,781
Trading securities
Assets:
Marketable Securities	489,938		480,845
Trading securities | TruPs
Assets:
Marketable Securities	489,938		480,845
Trading securities | Other securities
Assets:
Marketable Securities	0		0
Security-related receivables
Assets:
Marketable Securities	77,711		86,455
Security-related receivables | Trups Receivables
Assets:
Marketable Securities	7,683		8,211
Security-related receivables | Unsecured REIT note receivables
Assets:
Marketable Securities	32,532		33,046
Security-related receivables | CMBS receivables
Assets:
Marketable Securities	36,435	[1]	44,118	[2]
Security-related receivables | Other securities
Assets:
Marketable Securities	1,061		1,080
Available-for-sale Securities
Assets:
Marketable Securities	630		2
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative assets	0	[3]	0	[4]
Total assets	0	[3]	0	[4]
Liabilities:
Junior subordinated notes, at fair value	0	[3]	0	[4]
CDO notes payable, at fair value	0	[3]	0	[4]
Derivative liabilities	0	[3]	0	[4]
Warrants and investor SARs	0	[3]	0	[4]
Total liabilities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Trading securities | TruPs
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Trading securities | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Security-related receivables | Trups Receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Security-related receivables | Unsecured REIT note receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Security-related receivables | CMBS receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Security-related receivables | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | Available-for-sale Securities
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Other Observable Inputs (Level 2)
Assets:
Derivative assets	732	[3]	1,305	[4]
Total assets	71,390	[3]	79,551	[4]
Liabilities:
Junior subordinated notes, at fair value	0	[3]	0	[4]
CDO notes payable, at fair value	0	[3]	0	[4]
Derivative liabilities	28,098	[3]	45,926	[4]
Warrants and investor SARs	0	[3]	0	[4]
Total liabilities	28,098	[3]	45,926	[4]
Significant Other Observable Inputs (Level 2) | Trading securities | TruPs
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Other Observable Inputs (Level 2) | Trading securities | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | Trups Receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | Unsecured REIT note receivables
Assets:
Marketable Securities	32,532	[3]	33,046	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | CMBS receivables
Assets:
Marketable Securities	36,435	[3]	44,118	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | Other securities
Assets:
Marketable Securities	1,061	[3]	1,080	[4]
Significant Other Observable Inputs (Level 2) | Available-for-sale Securities
Assets:
Marketable Securities	630	[3]	2	[4]
Significant Unobservable Inputs (Level 3)
Assets:
Derivative assets	0	[3]	0	[4]
Total assets	497,621	[3]	489,056	[4]
Liabilities:
Junior subordinated notes, at fair value	13,048	[3]	11,911	[4]
CDO notes payable, at fair value	431,142	[3]	377,235	[4]
Derivative liabilities	53,900	[3]	67,405	[4]
Warrants and investor SARs	29,731	[3]	31,304	[4]
Total liabilities	527,821	[3]	487,855	[4]
Significant Unobservable Inputs (Level 3) | Trading securities | TruPs
Assets:
Marketable Securities	489,938	[3]	480,845	[4]
Significant Unobservable Inputs (Level 3) | Trading securities | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Unobservable Inputs (Level 3) | Security-related receivables | Trups Receivables
Assets:
Marketable Securities	7,683	[3]	8,211	[4]
Significant Unobservable Inputs (Level 3) | Security-related receivables | Unsecured REIT note receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Unobservable Inputs (Level 3) | Security-related receivables | CMBS receivables
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Unobservable Inputs (Level 3) | Security-related receivables | Other securities
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Unobservable Inputs (Level 3) | Available-for-sale Securities
Assets:
Marketable Securities	$ 0	[3]	$ 0	[4]

[1] CMBS receivables include securities with a fair value totaling $12,122 that are rated between "AAA" and "A-" by Standard & Poor's, securities with a fair value totaling $22,667 that are rated "BBB+" and "B-" by Standard & Poor's and securities with a fair value totaling $1,646 that are rated "D" by Standard & Poor's.

[2] CMBS receivables include securities with a fair value totaling $8,228 that are rated between "AAA" and "A-" by Standard & Poor's, securities with a fair value totaling $26,594 that are rated between "BBB+" and "B-" by Standard & Poor's, securities with a fair value totaling $8,164 that are rated "CCC" by Standard & Poor's, and securities with a fair value totaling $1,132 that are rated "D" by Standard & Poor's.

[3] During the nine-month period ended September 30, 2014, there were no transfers between Level 1 and Level 2, as well as, there were no transfers into and out of Level 3.

[4] During the year ended December 31, 2013, there were no transfers between Level 1 and Level 2, as well as, there were no transfers into and out of Level 3.