Loans Receivable and Allowance for Loan Losses (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	$ 82,526	$ 115,982
Past due 60-89 days	25,313	26,750
Past due 90 days or more	62,834	250,534
Total past due	170,673	393,266
Current	11,739,049	11,993,112
Total	11,909,722	12,386,378
Deferred loan origination costs	47,726	55,688
Loans receivable	11,957,448	12,442,066
Allowance for loan losses	(111,600)	(139,000)	(145,501)	(157,185)
Loans receivable, net	11,845,848	12,303,066
Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	77,097	107,754
Past due 60-89 days	22,852	24,154
Past due 90 days or more	4,093	384
Total past due	104,042	132,292
Current	11,681,961	11,922,468
Total	11,786,003	12,054,760
Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	5,429	8,228
Past due 60-89 days	2,461	2,596
Past due 90 days or more	58,741	250,150
Total past due	66,631	260,974
Current	57,088	70,644
Total	123,719	331,618
Consumer and other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	2,430	3,177
Past due 60-89 days	962	1,340
Past due 90 days or more	6,040	5,948
Total past due	9,432	10,465
Current	239,936	229,216
Total	249,368	239,681
Allowance for loan losses	(8,825)	(8,824)	(6,316)	(3,800)
Consumer and other loans | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	2,430	3,177
Past due 60-89 days	962	1,340
Total past due	3,392	4,517
Current	239,936	229,184
Total	243,328	233,701
Consumer and other loans | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 90 days or more	6,040	5,948
Total past due	6,040	5,948
Current		32
Total	6,040	5,980
Consumer and other loans | Home equity and other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	2,430	3,177
Past due 60-89 days	962	1,340
Past due 90 days or more	6,040	5,948
Total past due	9,432	10,465
Current	175,121	198,458
Total	184,553	208,923
Consumer and other loans | Home equity and other consumer | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	2,430	3,177
Past due 60-89 days	962	1,340
Total past due	3,392	4,517
Current	175,121	198,426
Total	178,513	202,943
Consumer and other loans | Home equity and other consumer | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 90 days or more	6,040	5,948
Total past due	6,040	5,948
Current		32
Total	6,040	5,980
Consumer and other loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	64,815	30,758
Total	64,815	30,758
Consumer and other loans | Commercial and industrial | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	64,815	30,758
Total	64,815	30,758
Mortgage loans (gross)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	80,096	112,805
Past due 60-89 days	24,351	25,410
Past due 90 days or more	56,794	244,586
Total past due	161,241	382,801
Current	11,499,113	11,763,896
Total	11,660,354	12,146,697
Mortgage loans (gross) | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	74,667	104,577
Past due 60-89 days	21,890	22,814
Past due 90 days or more	4,093	384
Total past due	100,650	127,775
Current	11,442,025	11,693,284
Total	11,542,675	11,821,059
Mortgage loans (gross) | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	5,429	8,228
Past due 60-89 days	2,461	2,596
Past due 90 days or more	52,701	244,202
Total past due	60,591	255,026
Current	57,088	70,612
Total	117,679	325,638
Mortgage loans (gross) | Residential mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	73,326	96,302
Past due 60-89 days	21,290	22,393
Past due 90 days or more	44,989	234,378
Total past due	139,605	353,073
Current	6,733,931	7,684,203
Total	6,873,536	8,037,276
Allowance for loan losses	(46,283)	(80,337)	(89,267)	(105,991)
Mortgage loans (gross) | Residential mortgage loans | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	69,335	90,108
Past due 60-89 days	19,175	20,154
Past due 90 days or more	144	151
Total past due	88,654	110,413
Current	6,684,871	7,621,388
Total	6,773,525	7,731,801
Mortgage loans (gross) | Residential mortgage loans | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	3,991	6,194
Past due 60-89 days	2,115	2,239
Past due 90 days or more	44,845	234,227
Total past due	50,951	242,660
Current	49,060	62,815
Total	100,011	305,475
Mortgage loans (gross) | Residential mortgage loans | Full documentation interest-only loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	16,314	29,476
Past due 60-89 days	7,690	5,802
Past due 90 days or more	11,502	78,271
Total past due	35,506	113,549
Current	818,676	1,268,652
Total	854,182	1,382,201
Mortgage loans (gross) | Residential mortgage loans | Full documentation interest-only loans | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	13,943	27,291
Past due 60-89 days	7,332	5,220
Total past due	21,275	32,511
Current	804,880	1,249,462
Total	826,155	1,281,973
Mortgage loans (gross) | Residential mortgage loans | Full documentation interest-only loans | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	2,371	2,185
Past due 60-89 days	358	582
Past due 90 days or more	11,502	78,271
Total past due	14,231	81,038
Current	13,796	19,190
Total	28,027	100,228
Mortgage loans (gross) | Residential mortgage loans | Full documentation amortizing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	26,082	32,516
Past due 60-89 days	7,849	8,068
Past due 90 days or more	14,355	42,085
Total past due	48,286	82,669
Current	4,955,407	5,336,788
Total	5,003,693	5,419,457
Mortgage loans (gross) | Residential mortgage loans | Full documentation amortizing loans | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	25,878	31,189
Past due 60-89 days	7,611	7,415
Past due 90 days or more	144	151
Total past due	33,633	38,755
Current	4,948,391	5,325,944
Total	4,982,024	5,364,699
Mortgage loans (gross) | Residential mortgage loans | Full documentation amortizing loans | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	204	1,327
Past due 60-89 days	238	653
Past due 90 days or more	14,211	41,934
Total past due	14,653	43,914
Current	7,016	10,844
Total	21,669	54,758
Mortgage loans (gross) | Residential mortgage loans | Reduced documentation interest-only loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	19,310	24,700
Past due 60-89 days	3,037	5,787
Past due 90 days or more	16,289	87,910
Total past due	38,636	118,397
Current	572,372	721,264
Total	611,008	839,661
Mortgage loans (gross) | Residential mortgage loans | Reduced documentation interest-only loans | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	18,490	22,635
Past due 60-89 days	2,584	5,208
Total past due	21,074	27,843
Current	547,350	693,660
Total	568,424	721,503
Mortgage loans (gross) | Residential mortgage loans | Reduced documentation interest-only loans | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	820	2,065
Past due 60-89 days	453	579
Past due 90 days or more	16,289	87,910
Total past due	17,562	90,554
Current	25,022	27,604
Total	42,584	118,158
Mortgage loans (gross) | Residential mortgage loans | Reduced documentation amortizing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	11,620	9,610
Past due 60-89 days	2,714	2,736
Past due 90 days or more	2,843	26,112
Total past due	17,177	38,458
Current	387,476	357,499
Total	404,653	395,957
Mortgage loans (gross) | Residential mortgage loans | Reduced documentation amortizing loans | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	11,024	8,993
Past due 60-89 days	1,648	2,311
Total past due	12,672	11,304
Current	384,250	352,322
Total	396,922	363,626
Mortgage loans (gross) | Residential mortgage loans | Reduced documentation amortizing loans | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	596	617
Past due 60-89 days	1,066	425
Past due 90 days or more	2,843	26,112
Total past due	4,505	27,154
Current	3,226	5,177
Total	7,731	32,331
Mortgage loans (gross) | Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	4,294	13,844
Past due 60-89 days	2,568	1,327
Past due 90 days or more	8,917	9,054
Total past due	15,779	24,225
Current	3,897,274	3,272,230
Total	3,913,053	3,296,455
Allowance for loan losses	(39,250)	(36,703)	(35,514)	(35,422)
Mortgage loans (gross) | Multi-family | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	3,646	12,740
Past due 60-89 days	2,222	970
Past due 90 days or more	1,790
Total past due	7,658	13,710
Current	3,893,539	3,270,206
Total	3,901,197	3,283,916
Mortgage loans (gross) | Multi-family | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	648	1,104
Past due 60-89 days	346	357
Past due 90 days or more	7,127	9,054
Total past due	8,121	10,515
Current	3,735	2,024
Total	11,856	12,539
Mortgage loans (gross) | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	2,476	2,659
Past due 60-89 days	493	1,690
Past due 90 days or more	2,888	1,154
Total past due	5,857	5,503
Current	867,908	807,463
Total	873,765	812,966
Allowance for loan losses	(17,242)	(13,136)	(14,404)	(11,972)
Mortgage loans (gross) | Commercial real estate | Accruing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	1,686	1,729
Past due 60-89 days	493	1,690
Past due 90 days or more	2,159	233
Total past due	4,338	3,652
Current	863,615	801,690
Total	867,953	805,342
Mortgage loans (gross) | Commercial real estate | Non-accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due 30-59 days	790	930
Past due 90 days or more	729	921
Total past due	1,519	1,851
Current	4,293	5,773
Total	$ 5,812	$ 7,624