Fair Value Measurements - Summary of Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Mar. 30, 2016	Dec. 31, 2015
Assets
Loans held for sale	$ 547,827		$ 2,499,111
Pledged securities	75,225		72,190
Derivative assets	16,130		11,678
Liabilities
Derivative liabilities	7,563		1,333
Recurring
Assets
Loans held for sale	547,827		2,499,111
Pledged securities	75,225		72,190
Derivative assets	16,130		11,678
Total financial assets	639,182		2,582,979
Liabilities
Derivative liabilities	7,563		1,333
Total financial liabilities	7,563		1,333
Level 1 | Recurring
Assets
Pledged securities	75,225		72,190
Total financial assets	75,225		72,190
Level 2 | Recurring
Assets
Loans held for sale	547,827		2,499,111
Total financial assets	547,827		2,499,111
Liabilities
Derivative liabilities	1,011
Total financial liabilities	1,011
Level 3 | Recurring
Assets
Derivative assets	16,130		11,678
Total financial assets	16,130		11,678
Liabilities
Derivative liabilities	6,552		1,333
Total financial liabilities	6,552		$ 1,333
CMBX | Level 2 | Recurring
Derivative instruments
Notional amount outstanding	$ 0	$ 25,000