Exit Costs - Summary of expenses incurred to date by segment (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	$ 8			$ 0	$ 49	$ 0
Reorganization
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	5	$ 8	$ 17		30
Cumulative costs recognized in prior year					0
Estimate of remaining costs	8				8
Program expected costs	38				38
PLS exit program
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	3	8	8		19
Cumulative costs recognized in prior year					41
Estimate of remaining costs	30				30
Program expected costs	90				90
Operating segment | Mortgage Production | Reorganization
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	5	3	6		14
Cumulative costs recognized in prior year					0
Estimate of remaining costs	6				6
Program expected costs	20				20
Operating segment | Mortgage Production | PLS exit program
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	1	7	7		15
Cumulative costs recognized in prior year					33
Estimate of remaining costs	27				27
Program expected costs	75				75
Operating segment | Mortgage Servicing | Reorganization
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	0	0	2		2
Cumulative costs recognized in prior year					0
Estimate of remaining costs	1				1
Program expected costs	3				3
Other | Reorganization
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	0	5	9		14
Cumulative costs recognized in prior year					0
Estimate of remaining costs	1				1
Program expected costs	15				15
Other | PLS exit program
Restructuring Cost and Reserve [Line Items]
Costs incurred in current year	2	$ 1	$ 1		4
Cumulative costs recognized in prior year					8
Estimate of remaining costs	3				3
Program expected costs	$ 15				$ 15