Fair Value Measurements - Schedule of Carrying Amounts and the Fair Values of the Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Financial assets:
Cash and cash equivalents	$ 98,224	$ 136,988	$ 65,516	$ 113,354
Restricted cash	10,006	5,306
Pledged securities	75,225	72,190
Loans held for sale	547,827	2,499,111
Loans held for investment, net	190,551	231,493
Derivative assets	16,130	11,678
Financial liabilities:
Derivative liabilities	7,563	1,333
Warehouse notes payable	640,307	2,649,470
Note payable	164,388	164,462
Carrying Amount
Financial assets:
Cash and cash equivalents	98,224	136,988
Restricted cash	10,006	5,306
Pledged securities	75,225	72,190
Loans held for sale	547,827	2,499,111
Loans held for investment, net	190,551	231,493
Derivative assets	16,130	11,678
Total financial assets	937,963	2,956,766
Financial liabilities:
Derivative liabilities	7,563	1,333
Warehouse notes payable	640,307	2,649,470
Note payable	164,388	164,462
Total financial liabilities	812,258	2,815,265
Fair Value
Financial assets:
Cash and cash equivalents	98,224	136,988
Restricted cash	10,006	5,306
Pledged securities	75,225	72,190
Loans held for sale	547,827	2,499,111
Loans held for investment, net	191,822	233,370
Derivative assets	16,130	11,678
Total financial assets	939,234	2,958,643
Financial liabilities:
Derivative liabilities	7,563	1,333
Warehouse notes payable	642,196	2,652,011
Note payable	168,155	168,431
Total financial liabilities	$ 817,914	$ 2,821,775