Borrowings (Details 2) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Borrowings
Weighted Average Rate (as a percent)	2.46%	3.03%
Callable borrowings	$ 1,950,000,000	$ 1,950,000,000
Reverse repurchase agreements
Borrowings
Weighted Average Rate (as a percent)	3.87%	4.32%
Borrowings restructured with the counterparties	500,000,000
FHLB-NY advances | FHLB-NY
Borrowings
Weighted Average Rate (as a percent)	1.83%	2.07%
Borrowings restructured with the counterparties	850,000,000
Restructured Borrowings
Borrowings
Weighted Average Rate (as a percent)	3.46%
Borrowings restructured with the counterparties	1,350,000,000
Weighted average rate before restructuring of borrowings (as a percent)	4.40%
Weighted average remaining term before restructuring of borrowings	4 years
Weighted average remaining term	7 years
Restructured borrowings of which contractual call dates extended to 2017	950,000,000
Restructured borrowings of which contractual call dates extended to 2016	100,000,000
Restructured borrowings of which contractual call dates extended to 2015	$ 200,000,000