Borrowings - Summary of Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Amount
Borrowings, net	$ 3,964,222	$ 4,187,691
Weighted Average Rate
Total debt (as a percentage)	2.40%	2.26%
Reverse repurchase agreements
Amount
Reverse repurchase agreements	$ 1,100,000	$ 1,100,000	$ 1,100,000
Weighted Average Rate
Long-term debt (as a percentage)	3.62%	3.62%	3.87%
FHLB-NY advances | Federal Home Loan Bank of New York
Amount
FHLB-NY advances	$ 2,180,000	$ 2,384,000	$ 2,454,000
Weighted Average Rate
Long-term debt (as a percentage)	1.86%	1.72%	1.79%
Other borrowings, net
Amount
Other borrowings, net	$ 249,222	$ 248,691
Weighted Average Rate
Long-term debt (as a percentage)	5.00%	5.00%
Federal funds purchased
Amount
Federal funds purchased	$ 435,000	$ 455,000
Weighted Average Rate
Short-term debt (as a percentage)	0.57%	0.31%