Loans Receivable and Allowance for Loan Losses (Composition of Loans Receivable) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Loans receivable and allowance for loan losses
30-59 Days	$ 68,334	$ 82,526
60-89 Days	18,892	25,313
90 Days or More	55,504	62,834
Total Past Due	142,730	170,673
Current	11,633,110	11,739,049
Total	11,775,840	11,909,722
Net unamortized premiums and deferred loan origination costs	46,027	47,726
Loans receivable	11,821,867	11,957,448
Allowance for loan losses	(110,500)	(111,600)	(134,000)	(139,000)
Loans receivable, net	11,711,367	11,845,848
Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	61,865	77,097
60-89 Days	17,940	22,852
90 Days or More	0	4,093
Total Past Due	79,805	104,042
Current	11,577,156	11,681,961
Total	11,656,961	11,786,003
Non-accrual loans:
Loans receivable and allowance for loan losses
30-59 Days	6,469	5,429
60-89 Days	952	2,461
90 Days or More	55,504	58,741
Total Past Due	62,925	66,631
Current	55,954	57,088
Total	118,879	123,719
Consumer and Other Loans
Loans receivable and allowance for loan losses
30-59 Days	1,168	2,430
60-89 Days	767	962
90 Days or More	6,691	6,040
Total Past Due	8,626	9,432
Current	244,459	239,936
Total	253,085	249,368
Allowance for loan losses	(9,819)	(8,825)	(10,007)	(8,824)
Consumer and Other Loans | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	1,168	2,430
60-89 Days	767	962
Total Past Due	1,935	3,392
Current	244,314	239,936
Total	246,249	243,328
Consumer and Other Loans | Non-accrual loans:
Loans receivable and allowance for loan losses
90 Days or More	6,691	6,040
Total Past Due	6,691	6,040
Current	145	0
Total	6,836	6,040
Consumer and Other Loans | Home equity and other consumer
Loans receivable and allowance for loan losses
30-59 Days	1,168	2,430
60-89 Days	767	962
90 Days or More	6,691	6,040
Total Past Due	8,626	9,432
Current	169,565	175,121
Total	178,191	184,553
Consumer and Other Loans | Home equity and other consumer | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	1,168	2,430
60-89 Days	767	962
Total Past Due	1,935	3,392
Current	169,420	175,121
Total	171,355	178,513
Consumer and Other Loans | Home equity and other consumer | Non-accrual loans:
Loans receivable and allowance for loan losses
90 Days or More	6,691	6,040
Total Past Due	6,691	6,040
Current	145	0
Total	6,836	6,040
Consumer and Other Loans | Commercial and industrial
Loans receivable and allowance for loan losses
30-59 Days	0	0
60-89 Days	0	0
90 Days or More	0	0
Total Past Due	0	0
Current	74,894	64,815
Total	74,894	64,815
Consumer and Other Loans | Commercial and industrial | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	0	0
60-89 Days	0	0
Total Past Due	0	0
Current	74,894	64,815
Total	74,894	64,815
Consumer and Other Loans | Commercial and industrial | Non-accrual loans:
Loans receivable and allowance for loan losses
90 Days or More	0	0
Total Past Due	0	0
Total	0	0
Mortgage loans (gross)
Loans receivable and allowance for loan losses
30-59 Days	67,166	80,096
60-89 Days	18,125	24,351
90 Days or More	48,813	56,794
Total Past Due	134,104	161,241
Current	11,388,651	11,499,113
Total	11,522,755	11,660,354
Mortgage loans (gross) | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	60,697	74,667
60-89 Days	17,173	21,890
90 Days or More	0	4,093
Total Past Due	77,870	100,650
Current	11,332,842	11,442,025
Total	11,410,712	11,542,675
Mortgage loans (gross) | Non-accrual loans:
Loans receivable and allowance for loan losses
30-59 Days	6,469	5,429
60-89 Days	952	2,461
90 Days or More	48,813	52,701
Total Past Due	56,234	60,591
Current	55,809	57,088
Total	112,043	117,679
Mortgage loans (gross) | Residential
Loans receivable and allowance for loan losses
30-59 Days	58,611	73,326
60-89 Days	17,208	21,290
90 Days or More	46,749	44,989
Total Past Due	122,568	139,605
Current	6,538,332	6,733,931
Total	6,660,900	6,873,536
Allowance for loan losses	(43,481)	(46,283)	(74,717)	(80,337)
Mortgage loans (gross) | Residential | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	53,220	69,335
60-89 Days	16,659	19,175
90 Days or More		144
Total Past Due	69,879	88,654
Current	6,491,891	6,684,871
Total	6,561,770	6,773,525
Mortgage loans (gross) | Residential | Non-accrual loans:
Loans receivable and allowance for loan losses
30-59 Days	5,391	3,991
60-89 Days	549	2,115
90 Days or More	46,749	44,845
Total Past Due	52,689	50,951
Current	46,441	49,060
Total	99,130	100,011
Mortgage loans (gross) | Residential | Full documentation interest-only
Loans receivable and allowance for loan losses
30-59 Days	8,227	16,314
60-89 Days	3,796	7,690
90 Days or More	11,278	11,502
Total Past Due	23,301	35,506
Current	732,359	818,676
Total	755,660	854,182
Mortgage loans (gross) | Residential | Full documentation interest-only | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	7,894	13,943
60-89 Days	3,796	7,332
Total Past Due	11,690	21,275
Current	719,237	804,880
Total	730,927	826,155
Mortgage loans (gross) | Residential | Full documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
30-59 Days	333	2,371
60-89 Days	0	358
90 Days or More	11,278	11,502
Total Past Due	11,611	14,231
Current	13,122	13,796
Total	24,733	28,027
Mortgage loans (gross) | Residential | Full documentation amortizing
Loans receivable and allowance for loan losses
30-59 Days	28,633	26,082
60-89 Days	6,895	7,849
90 Days or More	16,478	14,355
Total Past Due	52,006	48,286
Current	4,865,886	4,955,407
Total	4,917,892	5,003,693
Mortgage loans (gross) | Residential | Full documentation amortizing | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	25,321	25,878
60-89 Days	6,707	7,611
90 Days or More		144
Total Past Due	32,028	33,633
Current	4,858,702	4,948,391
Total	4,890,730	4,982,024
Mortgage loans (gross) | Residential | Full documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
30-59 Days	3,312	204
60-89 Days	188	238
90 Days or More	16,478	14,211
Total Past Due	19,978	14,653
Current	7,184	7,016
Total	27,162	21,669
Mortgage loans (gross) | Residential | Reduced documentation interest-only
Loans receivable and allowance for loan losses
30-59 Days	11,899	19,310
60-89 Days	3,619	3,037
90 Days or More	14,231	16,289
Total Past Due	29,749	38,636
Current	536,840	572,372
Total	566,589	611,008
Mortgage loans (gross) | Residential | Reduced documentation interest-only | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	10,885	18,490
60-89 Days	3,355	2,584
Total Past Due	14,240	21,074
Current	512,426	547,350
Total	526,666	568,424
Mortgage loans (gross) | Residential | Reduced documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
30-59 Days	1,014	820
60-89 Days	264	453
90 Days or More	14,231	16,289
Total Past Due	15,509	17,562
Current	24,414	25,022
Total	39,923	42,584
Mortgage loans (gross) | Residential | Reduced documentation amortizing
Loans receivable and allowance for loan losses
30-59 Days	9,852	11,620
60-89 Days	2,898	2,714
90 Days or More	4,762	2,843
Total Past Due	17,512	17,177
Current	403,247	387,476
Total	420,759	404,653
Mortgage loans (gross) | Residential | Reduced documentation amortizing | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	9,120	11,024
60-89 Days	2,801	1,648
Total Past Due	11,921	12,672
Current	401,526	384,250
Total	413,447	396,922
Mortgage loans (gross) | Residential | Reduced documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
30-59 Days	732	596
60-89 Days	97	1,066
90 Days or More	4,762	2,843
Total Past Due	5,591	4,505
Current	1,721	3,226
Total	7,312	7,731
Mortgage loans (gross) | Multi-family
Loans receivable and allowance for loan losses
30-59 Days	7,094	4,294
60-89 Days	737	2,568
90 Days or More	2,064	8,917
Total Past Due	9,895	15,779
Current	3,981,011	3,897,274
Total	3,990,906	3,913,053
Allowance for loan losses	(40,082)	(39,250)	(34,578)	(36,703)
Mortgage loans (gross) | Multi-family | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	6,796	3,646
60-89 Days	334	2,222
90 Days or More	0	1,790
Total Past Due	7,130	7,658
Current	3,977,772	3,893,539
Total	3,984,902	3,901,197
Mortgage loans (gross) | Multi-family | Non-accrual loans:
Loans receivable and allowance for loan losses
30-59 Days	298	648
60-89 Days	403	346
90 Days or More	2,064	7,127
Total Past Due	2,765	8,121
Current	3,239	3,735
Total	6,004	11,856
Mortgage loans (gross) | Commercial real estate
Loans receivable and allowance for loan losses
30-59 Days	1,461	2,476
60-89 Days	180	493
90 Days or More		2,888
Total Past Due	1,641	5,857
Current	869,308	867,908
Total	870,949	873,765
Allowance for loan losses	(17,118)	(17,242)	(14,698)	(13,136)
Mortgage loans (gross) | Commercial real estate | Accruing loans:
Loans receivable and allowance for loan losses
30-59 Days	681	1,686
60-89 Days	180	493
90 Days or More		2,159
Total Past Due	861	4,338
Current	863,179	863,615
Total	864,040	867,953
Mortgage loans (gross) | Commercial real estate | Non-accrual loans:
Loans receivable and allowance for loan losses
30-59 Days	780	790
90 Days or More		729
Total Past Due	780	1,519
Current	6,129	4,293
Total	$ 6,909	$ 5,812