Commitments and Contingencies - Summary of Allowance for Loan Repurchases or Indemnifications (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Balance at beginning of period	$ 2,659	$ 2,156
Provision for loan repurchases or indemnifications	183	390
Balance at end of period	$ 2,842	$ 2,546