Transfers and Servicing of Mortgage Loans (Details) (USD $) In Millions, unless otherwise specified			6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Capitalized servicing rights	Jun. 30, 2012 Capitalized servicing rights
Transfers and Servicing of Mortgage Loans
Servicing portfolio	$ 228,637	$ 183,730	$ 133,061	$ 147,894
Activity in the loan servicing portfolio associated with capitalized servicing rights
Balance, beginning of period	228,637	183,730	140,381	147,088
Additions			13,438	17,445
Payoffs, sales and curtailments			(20,758)	(16,639)
Balance, end of period	$ 228,637	$ 183,730	$ 133,061	$ 147,894