Credit Risk (Details) $ in Millions		12 Months Ended
		Dec. 31, 2015 USD ($) loan	Dec. 31, 2014 USD ($) loan
Credit Risk
Period of origination of loans within which they are sold to investors		30 days
Loan Servicing Portfolio Composition
Total servicing portfolio		$ 226,259	$ 227,272
Weighted-average interest rate (as a percent)		3.80%	3.90%
Portfolio Delinquency
Number of Loans (as a percent)	[1]	3.48%	4.14%
Unpaid Balance (as a percent)	[1]	2.47%	3.01%
Foreclosure/real estate owned
Number of Loans (as a percent)	[1],[2]	1.74%	2.22%
Unpaid Balance (as a percent)	[1],[2]	1.51%	2.04%
Number of loans in foreclosure | loan		15,487	21,456
Unpaid principal balance of loans in foreclosure		$ 3,000	$ 4,100
30 days
Portfolio Delinquency
Number of Loans (as a percent)	[1]	2.22%	2.43%
Unpaid Balance (as a percent)	[1]	1.55%	1.75%
60 days
Portfolio Delinquency
Number of Loans (as a percent)	[1]	0.44%	0.58%
Unpaid Balance (as a percent)	[1]	0.30%	0.41%
90 or more days
Portfolio Delinquency
Number of Loans (as a percent)	[1]	0.82%	1.13%
Unpaid Balance (as a percent)	[1]	0.62%	0.85%
Conventional loans
Loan Servicing Portfolio Composition
Total servicing portfolio		$ 197,971	$ 195,184
Government loans
Loan Servicing Portfolio Composition
Total servicing portfolio		24,087	27,720
Home equity lines of credit
Loan Servicing Portfolio Composition
Total servicing portfolio		4,201	4,368
Owned
Loan Servicing Portfolio Composition
Total servicing portfolio		99,869	113,849
Subserviced
Loan Servicing Portfolio Composition
Total servicing portfolio		$ 126,390	$ 113,423

[1] Represents portfolio delinquencies as a percentage of the total number of loans and the total unpaid balance of the portfolio.

[2] As of December 31, 2015 and 2014, the total servicing portfolio included 15,487 and 21,456 of loans in foreclosure with an unpaid principal balance of $3.0 billion and $4.1 billion, respectively.