Loans Receivable and Allowance for Loan Losses (Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Balance at the beginning of the period	$ 110,500	$ 134,000	$ 111,600	$ 139,000
Provision charged (credited) to operations	(2,967)	(5,742)	(3,310)	(4,111)
Charge-offs	(1,791)	(13,631)	(4,281)	(22,466)
Recoveries	1,758	3,973	3,491	6,177
Balance at the end of the period	107,500	118,600	107,500	118,600
Consumer and Other Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at the beginning of the period	9,819	10,007	8,825	8,824
Provision charged (credited) to operations	(1,073)	(31)	161	1,950
Charge-offs	(86)	(527)	(435)	(1,424)
Recoveries	110	91	219	190
Balance at the end of the period	8,770	9,540	8,770	9,540
Mortgage loans (gross) | Residential
Allowance for Loan and Lease Losses [Roll Forward]
Balance at the beginning of the period	43,481	74,717	46,283	80,337
Provision charged (credited) to operations	1,497	(9,132)	(354)	(12,608)
Charge-offs	(1,602)	(12,834)	(3,359)	(16,927)
Recoveries	1,170	3,801	1,976	5,750
Balance at the end of the period	44,546	56,552	44,546	56,552
Mortgage loans (gross) | Multi-family
Allowance for Loan and Lease Losses [Roll Forward]
Balance at the beginning of the period	40,082	34,578	39,250	36,703
Provision charged (credited) to operations	(1,663)	2,686	(1,407)	1,274
Charge-offs	(103)	(270)	(345)	(1,139)
Recoveries	478	81	1,296	237
Balance at the end of the period	38,794	37,075	38,794	37,075
Mortgage loans (gross) | Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at the beginning of the period	17,118	14,698	17,242	13,136
Provision charged (credited) to operations	(1,728)	735	(1,710)	5,273
Charge-offs	0	0	(142)	(2,976)
Recoveries		0		0
Balance at the end of the period	$ 15,390	$ 15,433	$ 15,390	$ 15,433