Fair Value - Schedule of Significant Unobservable Inputs Used in Fair Value Measurement of Real Estate Owned (Detail) - Non-Recurring Measurement Basis - Real Estate Owned, Net	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	0.00%	0.00%
Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	85.91%	61.61%
Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	6.80%	7.30%