Loans Receivable and Allowance for Loan Losses (Details) (USD $)	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Loans receivable and allowance for loan losses
30-59 Days Past Due	$ 105,939,000		$ 146,782,000
60-89 Days Past Due	32,184,000		37,637,000
90 Days or More	263,355,000		301,407,000
Total Past Due	401,478,000		485,826,000
Current	12,082,019,000		12,670,088,000
Total loans	12,483,497,000		13,155,914,000
Net unamortized premiums and deferred loan origination costs	58,046,000		68,058,000
Loans receivable	12,541,543,000		13,223,972,000
Allowance for loan losses	(143,000,000)	(143,900,000)	(145,501,000)	(148,472,000)	(148,102,000)	(157,185,000)
Loans receivable, net	12,398,543,000		13,078,471,000
Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	98,039,000		144,932,000
60-89 Days Past Due	29,037,000		36,947,000
90 Days or More	55,000		328,000
Total Past Due	127,131,000		182,207,000
Current	12,005,168,000		12,658,949,000
Total loans	12,132,299,000		12,841,156,000
Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	7,900,000		1,850,000
60-89 Days Past Due	3,147,000		690,000
90 Days or More	263,300,000		301,079,000
Total Past Due	274,347,000		303,619,000
Current	76,851,000		11,139,000
Total loans	351,198,000		314,758,000
Mortgage Loans (Gross)
Loans receivable and allowance for loan losses
30-59 Days Past Due	103,306,000		143,559,000
60-89 Days Past Due	30,798,000		36,322,000
90 Days or More	256,881,000		294,899,000
Total Past Due	390,985,000		474,780,000
Current	11,848,367,000		12,417,040,000
Total loans	12,239,352,000		12,891,820,000
Mortgage Loans (Gross) | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	95,406,000		141,709,000
60-89 Days Past Due	27,651,000		35,632,000
90 Days or More	55,000		328,000
Total Past Due	123,112,000		177,669,000
Current	11,771,548,000		12,405,901,000
Total loans	11,894,660,000		12,583,570,000
Mortgage Loans (Gross) | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	7,900,000		1,850,000
60-89 Days Past Due	3,147,000		690,000
90 Days or More	256,826,000		294,571,000
Total Past Due	267,873,000		297,111,000
Current	76,819,000		11,139,000
Total loans	344,692,000		308,250,000
Mortgage Loans (Gross) | Residential
Loans receivable and allowance for loan losses
30-59 Days Past Due	93,315,000		108,280,000
60-89 Days Past Due	27,026,000		27,814,000
90 Days or More	244,691,000		280,671,000
Total Past Due	365,032,000		416,765,000
Current	7,933,486,000		9,294,461,000
Total loans	8,298,518,000		9,711,226,000
Allowance for loan losses	(83,424,000)	(78,788,000)	(89,267,000)	(90,764,000)	(87,394,000)	(105,991,000)
Mortgage Loans (Gross) | Residential | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	86,445,000		106,430,000
60-89 Days Past Due	25,179,000		27,124,000
Total Past Due	111,624,000		133,554,000
Current	7,868,476,000		9,286,621,000
Total loans	7,980,100,000		9,420,175,000
Mortgage Loans (Gross) | Residential | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	6,870,000		1,850,000
60-89 Days Past Due	1,847,000		690,000
90 Days or More	244,691,000		280,671,000
Total Past Due	253,408,000		283,211,000
Current	65,010,000		7,840,000
Total loans	318,418,000		291,051,000
Mortgage Loans (Gross) | Residential | Full documentation interest-only loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	25,342,000		30,520,000
60-89 Days Past Due	6,327,000		9,650,000
90 Days or More	85,019,000		97,907,000
Total Past Due	116,688,000		138,077,000
Current	1,409,149,000		1,863,319,000
Total loans	1,525,837,000		2,001,396,000
Mortgage Loans (Gross) | Residential | Full documentation interest-only loans | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	23,479,000		30,520,000
60-89 Days Past Due	6,327,000		8,973,000
Total Past Due	29,806,000		39,493,000
Current	1,387,347,000		1,862,382,000
Total loans	1,417,153,000		1,901,875,000
Mortgage Loans (Gross) | Residential | Full documentation interest-only loans | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	1,863,000
60-89 Days Past Due			677,000
90 Days or More	85,019,000		97,907,000
Total Past Due	86,882,000		98,584,000
Current	21,802,000		937,000
Total loans	108,684,000		99,521,000
Mortgage Loans (Gross) | Residential | Full documentation amortizing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	30,293,000		36,281,000
60-89 Days Past Due	10,849,000		6,564,000
90 Days or More	42,294,000		43,014,000
Total Past Due	83,436,000		85,859,000
Current	5,417,588,000		6,219,013,000
Total loans	5,501,024,000		6,304,872,000
Mortgage Loans (Gross) | Residential | Full documentation amortizing loans | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	29,947,000		35,918,000
60-89 Days Past Due	9,623,000		6,564,000
Total Past Due	39,570,000		42,482,000
Current	5,408,913,000		6,218,064,000
Total loans	5,448,483,000		6,260,546,000
Mortgage Loans (Gross) | Residential | Full documentation amortizing loans | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	346,000		363,000
60-89 Days Past Due	1,226,000
90 Days or More	42,294,000		43,014,000
Total Past Due	43,866,000		43,377,000
Current	8,675,000		949,000
Total loans	52,541,000		44,326,000
Mortgage Loans (Gross) | Residential | Reduced documentation interest-only loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	27,513,000		29,254,000
60-89 Days Past Due	7,724,000		7,694,000
90 Days or More	91,089,000		107,254,000
Total Past Due	126,326,000		144,202,000
Current	753,220,000		861,093,000
Total loans	879,546,000		1,005,295,000
Mortgage Loans (Gross) | Residential | Reduced documentation interest-only loans | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	24,384,000		28,212,000
60-89 Days Past Due	7,232,000		7,694,000
Total Past Due	31,616,000		35,906,000
Current	723,406,000		855,907,000
Total loans	755,022,000		891,813,000
Mortgage Loans (Gross) | Residential | Reduced documentation interest-only loans | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	3,129,000		1,042,000
60-89 Days Past Due	492,000
90 Days or More	91,089,000		107,254,000
Total Past Due	94,710,000		108,296,000
Current	29,814,000		5,186,000
Total loans	124,524,000		113,482,000
Mortgage Loans (Gross) | Residential | Reduced documentation amortizing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	10,167,000		12,225,000
60-89 Days Past Due	2,126,000		3,906,000
90 Days or More	26,289,000		32,496,000
Total Past Due	38,582,000		48,627,000
Current	353,529,000		351,036,000
Total loans	392,111,000		399,663,000
Mortgage Loans (Gross) | Residential | Reduced documentation amortizing loans | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	8,635,000		11,780,000
60-89 Days Past Due	1,997,000		3,893,000
Total Past Due	10,632,000		15,673,000
Current	348,810,000		350,268,000
Total loans	359,442,000		365,941,000
Mortgage Loans (Gross) | Residential | Reduced documentation amortizing loans | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	1,532,000		445,000
60-89 Days Past Due	129,000		13,000
90 Days or More	26,289,000		32,496,000
Total Past Due	27,950,000		32,954,000
Current	4,719,000		768,000
Total loans	32,669,000		33,722,000
Mortgage Loans (Gross) | Multi-Family
Loans receivable and allowance for loan losses
30-59 Days Past Due	9,991,000		21,743,000
60-89 Days Past Due	1,811,000		5,382,000
90 Days or More	11,037,000		7,359,000
Total Past Due	22,839,000		34,484,000
Current	3,095,175,000		2,372,194,000
Total loans	3,118,014,000		2,406,678,000
Allowance for loan losses	(38,245,000)	(40,865,000)	(35,514,000)	(40,863,000)	(48,142,000)	(35,422,000)
Mortgage Loans (Gross) | Multi-Family | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	8,961,000		21,743,000
60-89 Days Past Due	1,448,000		5,382,000
Total Past Due	10,409,000		27,125,000
Current	3,091,944,000		2,368,895,000
Total loans	3,102,353,000		2,396,020,000
Mortgage Loans (Gross) | Multi-Family | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	1,030,000
60-89 Days Past Due	363,000
90 Days or More	11,037,000		7,359,000
Total Past Due	12,430,000		7,359,000
Current	3,231,000		3,299,000
Total loans	15,661,000		10,658,000
Mortgage Loans (Gross) | Commercial Real Estate
Loans receivable and allowance for loan losses
30-59 Days Past Due			13,536,000
60-89 Days Past Due	1,961,000		3,126,000
90 Days or More	1,153,000		6,869,000
Total Past Due	3,114,000		23,531,000
Current	819,706,000		750,385,000
Total loans	822,820,000		773,916,000
Allowance for loan losses	(14,004,000)	(16,642,000)	(14,404,000)	(11,558,000)	(9,109,000)	(11,972,000)
Mortgage Loans (Gross) | Commercial Real Estate | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due			13,536,000
60-89 Days Past Due	1,024,000		3,126,000
90 Days or More	55,000		328,000
Total Past Due	1,079,000		16,990,000
Current	811,128,000		750,385,000
Total loans	812,207,000		767,375,000
Mortgage Loans (Gross) | Commercial Real Estate | Non-accrual loans
Loans receivable and allowance for loan losses
60-89 Days Past Due	937,000
90 Days or More	1,098,000		6,541,000
Total Past Due	2,035,000		6,541,000
Current	8,578,000
Total loans	10,613,000		6,541,000
Consumer and Other Loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	2,633,000		3,223,000
60-89 Days Past Due	1,386,000		1,315,000
90 Days or More	6,474,000		6,508,000
Total Past Due	10,493,000		11,046,000
Current	233,652,000		253,048,000
Total loans	244,145,000		264,094,000
Allowance for loan losses	(7,327,000)	(7,605,000)	(6,316,000)	(5,287,000)	(3,457,000)	(3,800,000)
Consumer and Other Loans | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	2,633,000		3,223,000
60-89 Days Past Due	1,386,000		1,315,000
Total Past Due	4,019,000		4,538,000
Current	233,620,000		253,048,000
Total loans	237,639,000		257,586,000
Consumer and Other Loans | Non-accrual loans
Loans receivable and allowance for loan losses
90 Days or More	6,474,000		6,508,000
Total Past Due	6,474,000		6,508,000
Current	32,000
Total loans	6,506,000		6,508,000
Consumer and Other Loans | Home equity lines of credit
Loans receivable and allowance for loan losses
30-59 Days Past Due	2,573,000		3,103,000
60-89 Days Past Due	1,350,000		1,092,000
90 Days or More	6,441,000		6,459,000
Total Past Due	10,364,000		10,654,000
Current	196,153,000		221,266,000
Total loans	206,517,000		231,920,000
Consumer and Other Loans | Home equity lines of credit | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	2,573,000		3,103,000
60-89 Days Past Due	1,350,000		1,092,000
Total Past Due	3,923,000		4,195,000
Current	196,121,000		221,266,000
Total loans	200,044,000		225,461,000
Consumer and Other Loans | Home equity lines of credit | Non-accrual loans
Loans receivable and allowance for loan losses
90 Days or More	6,441,000		6,459,000
Total Past Due	6,441,000		6,459,000
Current	32,000
Total loans	6,473,000		6,459,000
Consumer and Other Loans | Other Loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	60,000		120,000
60-89 Days Past Due	36,000		223,000
90 Days or More	33,000		49,000
Total Past Due	129,000		392,000
Current	37,499,000		31,782,000
Total loans	37,628,000		32,174,000
Consumer and Other Loans | Other Loans | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	60,000		120,000
60-89 Days Past Due	36,000		223,000
Total Past Due	96,000		343,000
Current	37,499,000		31,782,000
Total loans	37,595,000		32,125,000
Consumer and Other Loans | Other Loans | Non-accrual loans
Loans receivable and allowance for loan losses
90 Days or More	33,000		49,000
Total Past Due	33,000		49,000
Total loans	$ 33,000		$ 49,000