Exit Costs - Summary of Expenses Incurred to Date by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	$ 62	$ 41	$ 0
PLS exit program
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	27
Cumulative costs recognized in prior years	41
Estimate of remaining costs	22
Total program costs	90
Reorganization
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	35
Cumulative costs recognized in prior years	0
Estimate of remaining costs	2
Total program costs	37
Other | PLS exit program
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	7
Cumulative costs recognized in prior years	8
Estimate of remaining costs	5
Total program costs	20
Other | Reorganization
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	15
Cumulative costs recognized in prior years	0
Estimate of remaining costs	0
Total program costs	15
Mortgage Production Segment | Operating segment | PLS exit program
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	20
Cumulative costs recognized in prior years	33
Estimate of remaining costs	17
Total program costs	70
Mortgage Production Segment | Operating segment | Reorganization
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	18
Cumulative costs recognized in prior years	0
Estimate of remaining costs	1
Total program costs	19
Mortgage Servicing segment | Operating segment | Reorganization
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	2
Cumulative costs recognized in prior years	0
Estimate of remaining costs	1
Total program costs	$ 3