Servicing Activities - Total Servicing Portfolio (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Loan Servicing Portfolio [Abstract]
MSRs, UPB	$ 151,482	$ 174,642
MSRs, Fair Value	500	690
Capitalized MSRs owned
Loan Servicing Portfolio [Abstract]
MSRs, UPB	8,906	84,657
MSRs, Fair Value	60	690
Capitalized MSRs under secured borrowing arrangements and subserviced
Loan Servicing Portfolio [Abstract]
MSRs, UPB	51,465	0
MSRs, Fair Value	440	0
Capitalized MSRs
Loan Servicing Portfolio [Abstract]
MSRs, UPB	60,371	84,657
MSRs, Fair Value	500	690
Subserviced
Loan Servicing Portfolio [Abstract]
MSRs, UPB	90,354	89,170
Other owned servicing
Loan Servicing Portfolio [Abstract]
MSRs, UPB	$ 757	$ 815