Fair Value Measurements (Details 5) (USD $)				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Mortgage loans held-for-sale Minimum	Dec. 31, 2012 Mortgage loans held-for-sale Maximum	Dec. 31, 2012 Total Fair Value	Dec. 31, 2011 Total Fair Value	Dec. 31, 2012 Level 2 Fair Value	Dec. 31, 2011 Level 2 Fair Value	Dec. 31, 2012 Level 3 Fair Value	Dec. 31, 2011 Level 3 Fair Value	Dec. 31, 2012 Carrying Value	Dec. 31, 2011 Carrying Value
Financial Assets:
Securities held-to-maturity	$ 1,700,141,000	$ 2,130,804,000				$ 1,725,090,000	$ 2,176,925,000	$ 1,725,090,000	$ 2,176,925,000			$ 1,700,141,000	$ 2,130,804,000
FHLB-NY stock	171,194,000	131,667,000				171,194,000	131,667,000	171,194,000	131,667,000			171,194,000	131,667,000
Loans held-for-sale, net						78,486,000	32,611,000			78,486,000	32,611,000	76,306,000	32,394,000
Loans receivable, net						13,311,997,000	13,368,354,000			13,311,997,000	13,368,354,000	13,078,471,000	13,117,419,000
MSR, net	6,947,000	8,136,000	9,204,000			6,948,000	8,137,000			6,948,000	8,137,000	6,947,000	8,136,000
Mortgage loan, original term				15 years	30 years
Financial Liabilities:
Deposits						10,588,073,000	11,416,033,000	10,588,073,000	11,416,033,000			10,443,958,000	11,245,614,000
Borrowings, net						$ 4,857,989,000	$ 4,624,636,000	$ 4,857,989,000	$ 4,624,636,000			$ 4,373,496,000	$ 4,121,573,000