Fair Value Measurements - Schedule of Carrying Amounts and the Fair Values of the Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Financial assets:
Cash and cash equivalents	$ 60,993	$ 136,988	$ 67,789	$ 113,354
Restricted cash	17,611	5,306
Pledged securities	78,491	72,190
Loans held for sale	2,244,329	2,499,111
Loans held for investment, net	239,861	231,493
Derivative assets	28,358	11,678
Financial liabilities:
Derivative liabilities	29,483	1,333
Warehouse notes payable	2,336,925	2,649,470
Note payable	164,313	164,462
Carrying Amount
Financial assets:
Cash and cash equivalents	60,993	136,988
Restricted cash	17,611	5,306
Pledged securities	78,491	72,190
Loans held for sale	2,244,329	2,499,111
Loans held for investment, net	239,861	231,493
Derivative assets	28,358	11,678
Total financial assets	2,669,643	2,956,766
Financial liabilities:
Derivative liabilities	29,483	1,333
Warehouse notes payable	2,336,925	2,649,470
Note payable	164,313	164,462
Total financial liabilities	2,530,721	2,815,265
Fair Value
Financial assets:
Cash and cash equivalents	60,993	136,988
Restricted cash	17,611	5,306
Pledged securities	78,491	72,190
Loans held for sale	2,244,329	2,499,111
Loans held for investment, net	242,092	233,370
Derivative assets	28,358	11,678
Total financial assets	2,671,874	2,958,643
Financial liabilities:
Derivative liabilities	29,483	1,333
Warehouse notes payable	2,339,241	2,652,011
Note payable	167,879	168,431
Total financial liabilities	$ 2,536,603	$ 2,821,775