Debt Obligations - Additional Information (Detail)	3 Months Ended		0 Months Ended	3 Months Ended	0 Months Ended	3 Months Ended		3 Months Ended				3 Months Ended						3 Months Ended										3 Months Ended									0 Months Ended	3 Months Ended		3 Months Ended			3 Months Ended
	Mar. 31, 2014 USD ($) Facility	Dec. 31, 2013 USD ($)	Nov. 30, 2013 Convertible Senior Notes [Member] USD ($)	Mar. 31, 2014 Convertible Senior Notes [Member]	Nov. 30, 2013 Convertible Senior Notes [Member] Class A Common Stock [Member] USD ($)	Mar. 31, 2014 CT CDO I [Member] USD ($)	Dec. 31, 2013 CT CDO I [Member] USD ($)	Mar. 31, 2014 Maximum [Member]	Mar. 31, 2014 Minimum [Member] USD ($)	Mar. 31, 2014 Asset-Specific Repurchase Agreements [Member] USD ($)	Dec. 31, 2013 Asset-Specific Repurchase Agreements [Member] USD ($)	Mar. 31, 2014 Wells Fargo [Member] USD ($)	Mar. 13, 2014 Wells Fargo [Member] USD ($)	Jul. 30, 2013 Wells Fargo [Member] USD ($)	Jul. 08, 2013 Wells Fargo [Member] USD ($)	Jun. 07, 2013 Wells Fargo [Member] USD ($)	Mar. 13, 2014 Wells Fargo [Member] Maximum [Member]	Mar. 31, 2014 Wells Fargo [Member] June 30, 2013 Credit Facility [Member]	Mar. 31, 2014 Wells Fargo [Member] June 7, 2013 Credit Facility [Member]	Mar. 31, 2014 Wells Fargo [Member] March 13, 2014 Credit Facility [Member]	Mar. 31, 2014 Wells Fargo [Member] July 8, 2013 Credit Facility [Member]	Mar. 31, 2014 Weighted Average Cash Coupon [Member]	Mar. 31, 2014 Weighted-Average All-In Cost Of Credit [Member]	Mar. 31, 2014 Morgan Stanley [Member] USD ($)	Mar. 03, 2014 Morgan Stanley [Member] USD ($)	Mar. 03, 2013 Morgan Stanley [Member] GBP (£)	Mar. 03, 2014 Morgan Stanley [Member] Maximum [Member]	Mar. 31, 2014 JP Morgan [Member] USD ($)	Dec. 20, 2013 JP Morgan [Member] USD ($)	Dec. 20, 2013 JP Morgan [Member] GBP (£)	Jun. 28, 2013 JP Morgan [Member] USD ($)	Dec. 20, 2013 JP Morgan [Member] Mezzanine and Junior Mortgage Collateral [Member]	Jun. 28, 2013 JP Morgan [Member] Mezzanine and Junior Mortgage Collateral [Member]	Dec. 20, 2013 JP Morgan [Member] Maximum [Member] Senior Collateral [Member]	Jun. 28, 2013 JP Morgan [Member] Maximum [Member] Senior Collateral [Member]	Mar. 31, 2014 JP Morgan [Member] Asset-Specific Repurchase Agreements [Member] USD ($)	Sep. 30, 2013 JP Morgan [Member] Asset-Specific Repurchase Agreements [Member] Repurchase Agreements [Member] USD ($)	Mar. 31, 2014 Citibank [Member] USD ($)	Jun. 12, 2013 Citibank [Member] First Tranche [Member] USD ($)	Mar. 31, 2014 Citibank [Member] Second Tranche [Member]	Jul. 26, 2013 Citibank [Member] Second Tranche [Member] USD ($)	Jun. 12, 2013 Citibank [Member] Maximum [Member]	Mar. 31, 2014 Bank of America [Member] USD ($)	Sep. 23, 2013 Bank of America [Member] USD ($)	May 21, 2013 Bank of America [Member] USD ($)	May 21, 2013 Bank of America [Member] Maximum [Member] Senior Collateral [Member]	May 21, 2013 Bank of America [Member] Maximum [Member] Mezzanine and Junior Mortgage Collateral [Member]
Debt Instrument [Line Items]
Number of revolving repurchase facility closed	2
Proceeds from line of credit	$ 912,600,000
Aggregate borrowings	1,500,000,000
Description of interest rate						LIBOR plus 2.40%						LIBOR plus 2.07%						LIBOR plus 2.25%	LIBOR plus at 2.50%		LIBOR plus 4.00%	LIBOR plus 2.09% per annum	LIBOR plus 2.36% per annum	Three-month LIBOR plus 2.38%				LIBOR plus 2.25%										LIBOR plus 2.07%					LIBOR plus 1.80%
LIBOR basis spread on debt obligation						2.40%						2.07%						2.25%	2.50%		4.00%	2.09%	2.36%	2.38%				2.04%										2.07%					1.80%
Weighted-average initial maturity	2 years 3 months 18 days
Weighted average outstanding repurchase obligation	1,100,000,000
Facility size													500,000,000	59,800,000	32,000,000	250,000,000									412,600,000	250,000,000			252,500,000	153,000,000	250,000,000					71,600,000	112,000,000		250,000,000		250,000,000				250,000,000
Maturity period																		The initial maturity date of the facility is August 8, 2015, which may be extended pursuant to three one-year extension options, each of which may be exercised by us.	The initial maturity date of the facility is June 7, 2016, which may be extended pursuant to (i) two one-year extension options, each of which may be exercised by us, and (ii) an additional one-year extension option, contingent upon notice regarding the failure of the collateral mortgage loan to be repaid at its final maturity.	The repurchase agreement specifies a one-year availability period, during which new advances can be made and which availability period is renewable at the discretion of Wells Fargo.	The maturity date of the facility is August 9, 2014, which may be extended pursuant to a six-month extension option, which may be exercised by us.							The repurchase agreement specifies a one-year availability period, during which new advances can be made and which availability period is renewable at the discretion of JP Morgan.										The initial facility expiration date is June 12, 2016, which may be extended annually by us.		The second tranche is subject to a one-year 'availability period,' during which new financing transactions can be initiated			The initial maturity date of the facility is May 21, 2016, subject to two one-year extension options
Outstanding borrowings										1,529,788,000	1,109,353,000	139,300,000												66,000,000				430,000,000										307,200,000					364,800,000
Maximum advance rate												77.80%												80.00%				77.10%										74.70%					79.10%
Percentage of recourse debt																	25.00%										25.00%					100.00%	100.00%	25.00%	25.00%							25.00%				50.00%	100.00%
Master repurchase agreement, maturity date																									Mar. 03, 2017			Dec. 20, 2016
Maturity date																																					June 2014
Additional potential advances																																												250,000,000
Covenants, EBITDA to fixed charges								1.40	1.0
Covenants, minimum tangible net worth	717,100,000
Covenants, percentage of tangible assets on cash proceeds from equity issuances	75.00%
Covenants, minimum cash liquidity amount									10,000,000
Covenants, percentage of recourse indebtedness	5.00%
Covenants, indebtedness to total assets								83.33%
Convertible Senior Notes, Principal amount			172,500,000
Convertible Senior Notes, Interest rate			5.25%
Maturity Date				Dec. 01, 2018		Jul. 31, 2039
Convertible Senior Notes, Interest rate including underwriter discounts			5.87%
Debt conversion, converted instrument, common stock issued					34.8943
Debt conversion, convertible notes, principal amount					1,000
Debt instrument, convertible, conversion price					$ 28.66
Description of convertible notes conversion			The Convertible Notes are convertible, at the holders' option, into shares of our class A common stock at any time prior to the close of business on the business day immediately preceding September 1, 2018, subject to certain limitations, at the applicable conversion rate in effect on the conversion date.
Discount upon issuance of Convertible Notes			9,100,000
Convertible Notes, effective interest rate			6.50%
Convertible Senior Notes, Interest rate including amortization of discount upon issuance			7.16%
Securitized debt obligations	$ 39,394,000	$ 40,181,000				$ 39,394,000	$ 40,181,000