Loans Receivable and Allowance for Loan Losses (Composition of Loans Receivable) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Loans receivable and allowance for loan losses
Past due 90 days or more	$ 179,125		$ 170,673
Net unamortized premiums and deferred loan origination costs	43,002		47,726
Loans receivable	11,253,372		11,957,448
Allowance for loan losses	(103,500)	$ (107,500)	(111,600)	$ (113,600)	$ (118,600)	$ (139,000)
Loans receivable, net	11,149,872		11,845,848
Current	11,031,245		11,739,049
Total	11,210,370		11,909,722
Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	97,834		104,042
Current	10,983,224		11,681,961
Total	11,081,058		11,786,003
Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	81,291		66,631
Current	48,021		57,088
Total	129,312		123,719
Consumer and Other Loans
Loans receivable and allowance for loan losses
Past due 90 days or more	8,794		9,432
Allowance for loan losses	(8,974)	(8,770)	(8,825)	(9,426)	(9,540)	(8,824)
Current	239,860		239,936
Total	248,654		249,368
Consumer and Other Loans | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	2,585		3,392
Current	239,860		239,936
Total	242,445		243,328
Consumer and Other Loans | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	6,209		6,040
Current	0		0
Total	6,209		6,040
Consumer and Other Loans | Home equity and other consumer
Loans receivable and allowance for loan losses
Past due 90 days or more	8,794		9,432
Current	158,273		175,121
Total	167,067		184,553
Consumer and Other Loans | Home equity and other consumer | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	2,585		3,392
Current	158,273		175,121
Total	160,858		178,513
Consumer and Other Loans | Home equity and other consumer | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	6,209		6,040
Current	0		0
Total	6,209		6,040
Consumer and Other Loans | Commercial and industrial
Loans receivable and allowance for loan losses
Past due 90 days or more			0
Current	81,587		64,815
Total	81,587		64,815
Consumer and Other Loans | Commercial and industrial | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more			0
Current	81,587		64,815
Total	81,587		64,815
Consumer and Other Loans | Commercial and industrial | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more			0
Total			0
Mortgage loans (gross)
Loans receivable and allowance for loan losses
Past due 90 days or more	170,331		161,241
Current	10,791,385		11,499,113
Total	10,961,716		11,660,354
Mortgage loans (gross) | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	95,249		100,650
Current	10,743,364		11,442,025
Total	10,838,613		11,542,675
Mortgage loans (gross) | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	75,082		60,591
Current	48,021		57,088
Total	123,103		117,679
Mortgage loans (gross) | Residential
Loans receivable and allowance for loan losses
Past due 90 days or more	154,785		139,605
Allowance for loan losses	(42,241)	(44,546)	(46,283)	(49,332)	(56,552)	(80,337)
Current	6,072,682		6,733,931
Total	6,227,467		6,873,536
Mortgage loans (gross) | Residential | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	84,658		88,654
Current	6,028,940		6,684,871
Total	6,113,598		6,773,525
Mortgage loans (gross) | Residential | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	70,127		50,951
Current	43,742		49,060
Total	113,869		100,011
Mortgage loans (gross) | Residential | Full documentation interest-only
Loans receivable and allowance for loan losses
Past due 90 days or more	25,068		35,506
Current	511,163		818,676
Total	536,231		854,182
Mortgage loans (gross) | Residential | Full documentation interest-only | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	9,880		21,275
Current	501,991		804,880
Total	511,871		826,155
Mortgage loans (gross) | Residential | Full documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	15,188		14,231
Current	9,172		13,796
Total	24,360		28,027
Mortgage loans (gross) | Residential | Full documentation amortizing
Loans receivable and allowance for loan losses
Past due 90 days or more	67,718		48,286
Current	4,704,866		4,955,407
Total	4,772,584		5,003,693
Mortgage loans (gross) | Residential | Full documentation amortizing | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	38,480		33,633
Current	4,696,199		4,948,391
Total	4,734,679		4,982,024
Mortgage loans (gross) | Residential | Full documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	29,238		14,653
Current	8,667		7,016
Total	37,905		21,669
Mortgage loans (gross) | Residential | Reduced documentation interest-only
Loans receivable and allowance for loan losses
Past due 90 days or more	33,808		38,636
Current	362,624		572,372
Total	396,432		611,008
Mortgage loans (gross) | Residential | Reduced documentation interest-only | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	16,517		21,074
Current	345,582		547,350
Total	362,099		568,424
Mortgage loans (gross) | Residential | Reduced documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	17,291		17,562
Current	17,042		25,022
Total	34,333		42,584
Mortgage loans (gross) | Residential | Reduced documentation amortizing
Loans receivable and allowance for loan losses
Past due 90 days or more	28,191		17,177
Current	494,029		387,476
Total	522,220		404,653
Mortgage loans (gross) | Residential | Reduced documentation amortizing | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	19,781		12,672
Current	485,168		384,250
Total	504,949		396,922
Mortgage loans (gross) | Residential | Reduced documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	8,410		4,505
Current	8,861		3,226
Total	17,271		7,731
Mortgage loans (gross) | Multi-family
Loans receivable and allowance for loan losses
Past due 90 days or more	10,863		15,779
Allowance for loan losses	(38,866)	(38,794)	(39,250)	(38,307)	(37,075)	(36,703)
Current	3,897,905		3,897,274
Total	3,908,768		3,913,053
Mortgage loans (gross) | Multi-family | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	6,897		7,658
Current	3,896,917		3,893,539
Total	3,903,814		3,901,197
Mortgage loans (gross) | Multi-family | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	3,966		8,121
Current	988		3,735
Total	4,954		11,856
Mortgage loans (gross) | Commercial real estate
Loans receivable and allowance for loan losses
Past due 90 days or more	4,683		5,857
Allowance for loan losses	(13,419)	$ (15,390)	(17,242)	$ (16,535)	$ (15,433)	$ (13,136)
Current	820,798		867,908
Total	825,481		873,765
Mortgage loans (gross) | Commercial real estate | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	3,694		4,338
Current	817,507		863,615
Total	821,201		867,953
Mortgage loans (gross) | Commercial real estate | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	989		1,519
Current	3,291		4,293
Total	4,280		5,812
30-59 Days
Loans receivable and allowance for loan losses
Past due 90 days or more	80,626		82,526
30-59 Days | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	73,426		77,097
30-59 Days | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	7,200		5,429
30-59 Days | Consumer and Other Loans
Loans receivable and allowance for loan losses
Past due 90 days or more	2,189		2,430
30-59 Days | Consumer and Other Loans | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	2,189		2,430
30-59 Days | Consumer and Other Loans | Home equity and other consumer
Loans receivable and allowance for loan losses
Past due 90 days or more	2,189		2,430
30-59 Days | Consumer and Other Loans | Home equity and other consumer | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	2,189		2,430
30-59 Days | Consumer and Other Loans | Commercial and industrial
Loans receivable and allowance for loan losses
Past due 90 days or more			0
30-59 Days | Consumer and Other Loans | Commercial and industrial | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more			0
30-59 Days | Mortgage loans (gross)
Loans receivable and allowance for loan losses
Past due 90 days or more	78,437		80,096
30-59 Days | Mortgage loans (gross) | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	71,237		74,667
30-59 Days | Mortgage loans (gross) | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	7,200		5,429
30-59 Days | Mortgage loans (gross) | Residential
Loans receivable and allowance for loan losses
Past due 90 days or more	72,170		73,326
30-59 Days | Mortgage loans (gross) | Residential | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	65,961		69,335
30-59 Days | Mortgage loans (gross) | Residential | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	6,209		3,991
30-59 Days | Mortgage loans (gross) | Residential | Full documentation interest-only
Loans receivable and allowance for loan losses
Past due 90 days or more	8,030		16,314
30-59 Days | Mortgage loans (gross) | Residential | Full documentation interest-only | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	6,863		13,943
30-59 Days | Mortgage loans (gross) | Residential | Full documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	1,167		2,371
30-59 Days | Mortgage loans (gross) | Residential | Full documentation amortizing
Loans receivable and allowance for loan losses
Past due 90 days or more	31,186		26,082
30-59 Days | Mortgage loans (gross) | Residential | Full documentation amortizing | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	29,944		25,878
30-59 Days | Mortgage loans (gross) | Residential | Full documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	1,242		204
30-59 Days | Mortgage loans (gross) | Residential | Reduced documentation interest-only
Loans receivable and allowance for loan losses
Past due 90 days or more	14,251		19,310
30-59 Days | Mortgage loans (gross) | Residential | Reduced documentation interest-only | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	12,619		18,490
30-59 Days | Mortgage loans (gross) | Residential | Reduced documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	1,632		820
30-59 Days | Mortgage loans (gross) | Residential | Reduced documentation amortizing
Loans receivable and allowance for loan losses
Past due 90 days or more	18,703		11,620
30-59 Days | Mortgage loans (gross) | Residential | Reduced documentation amortizing | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	16,535		11,024
30-59 Days | Mortgage loans (gross) | Residential | Reduced documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	2,168		596
30-59 Days | Mortgage loans (gross) | Multi-family
Loans receivable and allowance for loan losses
Past due 90 days or more	4,268		4,294
30-59 Days | Mortgage loans (gross) | Multi-family | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	3,524		3,646
30-59 Days | Mortgage loans (gross) | Multi-family | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	744		648
30-59 Days | Mortgage loans (gross) | Commercial real estate
Loans receivable and allowance for loan losses
Past due 90 days or more	1,999		2,476
30-59 Days | Mortgage loans (gross) | Commercial real estate | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	1,752		1,686
30-59 Days | Mortgage loans (gross) | Commercial real estate | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	247		790
60-89 Days
Loans receivable and allowance for loan losses
Past due 90 days or more	25,884		25,313
60-89 Days | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	22,012		22,852
60-89 Days | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	3,872		2,461
60-89 Days | Consumer and Other Loans
Loans receivable and allowance for loan losses
Past due 90 days or more	396		962
60-89 Days | Consumer and Other Loans | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	396		962
60-89 Days | Consumer and Other Loans | Home equity and other consumer
Loans receivable and allowance for loan losses
Past due 90 days or more	396		962
60-89 Days | Consumer and Other Loans | Home equity and other consumer | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	396		962
60-89 Days | Consumer and Other Loans | Commercial and industrial
Loans receivable and allowance for loan losses
Past due 90 days or more			0
60-89 Days | Consumer and Other Loans | Commercial and industrial | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more			0
60-89 Days | Mortgage loans (gross)
Loans receivable and allowance for loan losses
Past due 90 days or more	25,488		24,351
60-89 Days | Mortgage loans (gross) | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	21,616		21,890
60-89 Days | Mortgage loans (gross) | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	3,872		2,461
60-89 Days | Mortgage loans (gross) | Residential
Loans receivable and allowance for loan losses
Past due 90 days or more	20,495		21,290
60-89 Days | Mortgage loans (gross) | Residential | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	18,555		19,175
60-89 Days | Mortgage loans (gross) | Residential | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	1,940		2,115
60-89 Days | Mortgage loans (gross) | Residential | Full documentation interest-only
Loans receivable and allowance for loan losses
Past due 90 days or more	3,017		7,690
60-89 Days | Mortgage loans (gross) | Residential | Full documentation interest-only | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	3,017		7,332
60-89 Days | Mortgage loans (gross) | Residential | Full documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more			358
60-89 Days | Mortgage loans (gross) | Residential | Full documentation amortizing
Loans receivable and allowance for loan losses
Past due 90 days or more	10,144		7,849
60-89 Days | Mortgage loans (gross) | Residential | Full documentation amortizing | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	8,394		7,611
60-89 Days | Mortgage loans (gross) | Residential | Full documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	1,750		238
60-89 Days | Mortgage loans (gross) | Residential | Reduced documentation interest-only
Loans receivable and allowance for loan losses
Past due 90 days or more	3,898		3,037
60-89 Days | Mortgage loans (gross) | Residential | Reduced documentation interest-only | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	3,898		2,584
60-89 Days | Mortgage loans (gross) | Residential | Reduced documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	0		453
60-89 Days | Mortgage loans (gross) | Residential | Reduced documentation amortizing
Loans receivable and allowance for loan losses
Past due 90 days or more	3,436		2,714
60-89 Days | Mortgage loans (gross) | Residential | Reduced documentation amortizing | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	3,246		1,648
60-89 Days | Mortgage loans (gross) | Residential | Reduced documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	190		1,066
60-89 Days | Mortgage loans (gross) | Multi-family
Loans receivable and allowance for loan losses
Past due 90 days or more	4,262		2,568
60-89 Days | Mortgage loans (gross) | Multi-family | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	2,882		2,222
60-89 Days | Mortgage loans (gross) | Multi-family | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	1,380		346
60-89 Days | Mortgage loans (gross) | Commercial real estate
Loans receivable and allowance for loan losses
Past due 90 days or more	731		493
60-89 Days | Mortgage loans (gross) | Commercial real estate | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	179		493
60-89 Days | Mortgage loans (gross) | Commercial real estate | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	552
90 Days or More
Loans receivable and allowance for loan losses
Past due 90 days or more	72,615		62,834
90 Days or More | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	2,396		4,093
90 Days or More | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	70,219		58,741
90 Days or More | Consumer and Other Loans
Loans receivable and allowance for loan losses
Past due 90 days or more	6,209		6,040
90 Days or More | Consumer and Other Loans | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	6,209		6,040
90 Days or More | Consumer and Other Loans | Home equity and other consumer
Loans receivable and allowance for loan losses
Past due 90 days or more	6,209		6,040
90 Days or More | Consumer and Other Loans | Home equity and other consumer | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	6,209		6,040
90 Days or More | Consumer and Other Loans | Commercial and industrial
Loans receivable and allowance for loan losses
Past due 90 days or more			0
90 Days or More | Consumer and Other Loans | Commercial and industrial | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more			0
90 Days or More | Mortgage loans (gross)
Loans receivable and allowance for loan losses
Past due 90 days or more	66,406		56,794
90 Days or More | Mortgage loans (gross) | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	2,396		4,093
90 Days or More | Mortgage loans (gross) | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	64,010		52,701
90 Days or More | Mortgage loans (gross) | Residential
Loans receivable and allowance for loan losses
Past due 90 days or more	62,120		44,989
90 Days or More | Mortgage loans (gross) | Residential | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	142		144
90 Days or More | Mortgage loans (gross) | Residential | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	61,978		44,845
90 Days or More | Mortgage loans (gross) | Residential | Full documentation interest-only
Loans receivable and allowance for loan losses
Past due 90 days or more	14,021		11,502
90 Days or More | Mortgage loans (gross) | Residential | Full documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	14,021		11,502
90 Days or More | Mortgage loans (gross) | Residential | Full documentation amortizing
Loans receivable and allowance for loan losses
Past due 90 days or more	26,388		14,355
90 Days or More | Mortgage loans (gross) | Residential | Full documentation amortizing | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	142		144
90 Days or More | Mortgage loans (gross) | Residential | Full documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	26,246		14,211
90 Days or More | Mortgage loans (gross) | Residential | Reduced documentation interest-only
Loans receivable and allowance for loan losses
Past due 90 days or more	15,659		16,289
90 Days or More | Mortgage loans (gross) | Residential | Reduced documentation interest-only | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	15,659		16,289
90 Days or More | Mortgage loans (gross) | Residential | Reduced documentation amortizing
Loans receivable and allowance for loan losses
Past due 90 days or more	6,052		2,843
90 Days or More | Mortgage loans (gross) | Residential | Reduced documentation amortizing | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	6,052		2,843
90 Days or More | Mortgage loans (gross) | Multi-family
Loans receivable and allowance for loan losses
Past due 90 days or more	2,333		8,917
90 Days or More | Mortgage loans (gross) | Multi-family | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	491		1,790
90 Days or More | Mortgage loans (gross) | Multi-family | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	1,842		7,127
90 Days or More | Mortgage loans (gross) | Commercial real estate
Loans receivable and allowance for loan losses
Past due 90 days or more	1,953		2,888
90 Days or More | Mortgage loans (gross) | Commercial real estate | Accruing loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	1,763		2,159
90 Days or More | Mortgage loans (gross) | Commercial real estate | Non-accrual loans:
Loans receivable and allowance for loan losses
Past due 90 days or more	$ 190		$ 729