Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financial Assets:
Securities held-to-maturity	$ 2,296,799	$ 2,133,804
FHLB-NY stock	131,137	140,754
MSR, net	11,014	11,401
Level 2
Financial Assets:
Securities held-to-maturity	2,286,092	2,131,371
FHLB-NY stock	131,137	140,754
Loans held-for-sale, net	0	0
Loans receivable, net	0	0
MSR, net	0	0
Financial Liabilities:
Deposits	9,123,740	9,534,918
Borrowings, net	4,132,940	4,395,604
Level 3
Financial Assets:
Securities held-to-maturity	0	0
FHLB-NY stock	0	0
Loans held-for-sale, net	9,037	7,955
Loans receivable, net	11,112,709	11,967,608
MSR, net	11,017	11,406
Financial Liabilities:
Deposits	0	0
Borrowings, net	0	0
Carrying Value
Financial Assets:
Securities held-to-maturity	2,296,799	2,133,804
FHLB-NY stock	131,137	140,754
Loans held-for-sale, net	8,960	7,640
Loans receivable, net	11,055,081	11,845,848
MSR, net	11,014	11,401
Financial Liabilities:
Deposits	9,106,027	9,504,909
Borrowings, net	3,964,222	4,187,691
Estimated Fair Value
Financial Assets:
Securities held-to-maturity	2,286,092	2,131,371
FHLB-NY stock	131,137	140,754
Loans held-for-sale, net	9,037	7,955
Loans receivable, net	11,112,709	11,967,608
MSR, net	11,017	11,406
Financial Liabilities:
Deposits	9,123,740	9,534,918
Borrowings, net	$ 4,132,940	$ 4,395,604