Information of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Assets:
Marketable Securities	$ 573,739		$ 567,302
Derivative assets	946		1,305
Total assets	574,685		568,607
Liabilities:
Junior subordinated notes	12,515		11,911
CDO notes payable, at fair value	399,448		377,235
Derivative liabilities	102,796		113,331
Warrants and investor SARs	41,004		31,304
Total liabilities	555,763		533,781
Trading securities
Assets:
Marketable Securities	486,748		480,845
Trading securities | TruPs
Assets:
Marketable Securities	486,748		480,845
Trading securities | Other securities
Assets:
Marketable Securities	0		0
Available-for-sale Securities
Assets:
Marketable Securities	2		2
Security-related receivables
Assets:
Marketable Securities	86,989		86,455
Security-related receivables | Trups Receivables
Assets:
Marketable Securities	8,390		8,211
Security-related receivables | Unsecured REIT note receivables
Assets:
Marketable Securities	33,066		33,046
Security-related receivables | CMBS receivables
Assets:
Marketable Securities	44,469	[1]	44,118	[2]
Security-related receivables | Other securities
Assets:
Marketable Securities	1,064		1,080
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	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) | Available-for-sale 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]
Significant Other Observable Inputs (Level 2)
Assets:
Derivative assets	946	[3]	1,305	[4]
Total assets	79,547	[3]	79,551	[4]
Liabilities:
Junior subordinated notes	0	[3]	0	[4]
CDO notes payable, at fair value	0	[3]	0	[4]
Derivative liabilities	39,975	[3]	45,926	[4]
Warrants and investor SARs	0	[3]	0	[4]
Total liabilities	39,975	[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) | Available-for-sale Securities
Assets:
Marketable Securities	2	[3]	2	[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	33,066	[3]	33,046	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | CMBS receivables
Assets:
Marketable Securities	44,469	[3]	44,118	[4]
Significant Other Observable Inputs (Level 2) | Security-related receivables | Other securities
Assets:
Marketable Securities	1,064	[3]	1,080	[4]
Significant Unobservable Inputs (Level 3)
Assets:
Derivative assets	0	[3]	0	[4]
Total assets	495,138	[3]	489,056	[4]
Liabilities:
Junior subordinated notes	12,515	[3]	11,911	[4]
CDO notes payable, at fair value	399,448	[3]	377,235	[4]
Derivative liabilities	62,821	[3]	67,405	[4]
Warrants and investor SARs	41,004	[3]	31,304	[4]
Total liabilities	515,788	[3]	487,855	[4]
Significant Unobservable Inputs (Level 3) | Trading securities | TruPs
Assets:
Marketable Securities	486,748	[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) | Available-for-sale Securities
Assets:
Marketable Securities	0	[3]	0	[4]
Significant Unobservable Inputs (Level 3) | Security-related receivables | Trups Receivables
Assets:
Marketable Securities	8,390	[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]

[1] CMBS receivables include securities with a fair value totaling $10,167 that are rated between "AAA" and "A-" by Standard & Poor's, securities with a fair value totaling $24,902 that are rated "BBB+" and "B-" by Standard & Poor's, securities with a fair value totaling $8,183 that are rated "CCC" by Standard & Poor's and securities with a fair value totaling $1,217 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 three-month period ended March 31, 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.