Fair Value Measurements - Schedule of Carrying Amounts and the Fair Values of the Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financial assets:
Cash and cash equivalents	$ 136,988	$ 113,354	$ 170,563	$ 65,027
Restricted cash	5,306	13,854
Pledged securities	72,190	67,719
Loans held for sale	2,499,111	1,072,116
Loans held for investment, net	231,493	223,059
Derivative assets	11,678	14,535
Financial liabilities:
Derivative liabilities	1,333	4,877
Warehouse notes payable	2,649,470	1,214,279
Note payable	164,462	169,095
Carrying Amount
Financial assets:
Cash and cash equivalents	136,988	113,354
Restricted cash	5,306	13,854
Pledged securities	72,190	67,719
Loans held for sale	2,499,111	1,072,116
Loans held for investment, net	231,493	223,059
Derivative assets	11,678	14,535
Total financial assets	2,956,766	1,504,637
Financial liabilities:
Derivative liabilities	1,333	4,877
Warehouse notes payable	2,649,470	1,214,279
Note payable	164,462	169,095
Total financial liabilities	2,815,265	1,388,251
Fair Value
Financial assets:
Cash and cash equivalents	136,988	113,354
Restricted cash	5,306	13,854
Pledged securities	72,190	67,719
Loans held for sale	2,499,111	1,072,116
Loans held for investment, net	233,370	225,318
Derivative assets	11,678	14,535
Total financial assets	2,958,643	1,506,896
Financial liabilities:
Derivative liabilities	1,333	4,877
Warehouse notes payable	2,652,011	1,216,245
Note payable	168,431	173,250
Total financial liabilities	$ 2,821,775	$ 1,394,372