Acquisition, Divestiture, and Discontinued Operations - Quantitative Information about Level 3 Fair Value Measurements (Detail) - Level 3 [Member] - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Portfolio Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Portfolio loans accounted for at fair value	$ 3	$ 4
Minimum [Member] | Portfolio Loan Indicative Bids [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Percentage of significant unobservable inputs	84.50%	84.50%
Maximum [Member] | Portfolio Loan Indicative Bids [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Percentage of significant unobservable inputs	104.00%	104.00%