Loans Receivable and Allowance for Loan Losses (Details) (USD $)	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Loans receivable and allowance for loan losses
30-59 Days Past Due	$ 114,328,000		$ 146,782,000
60-89 Days Past Due	39,641,000		37,637,000
90 Days or More	278,065,000		301,407,000
Total Past Due	432,034,000		485,826,000
Current	12,176,881,000		12,670,088,000
Total loans	12,608,915,000		13,155,914,000
Net unamortized premiums and deferred loan origination costs	60,167,000		68,058,000
Loans receivable	12,669,082,000		13,223,972,000
Allowance for loan losses	(143,900,000)	(144,250,000)	(145,501,000)	(148,102,000)	(149,899,000)	(157,185,000)
Loans receivable, net	12,525,182,000		13,078,471,000
Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	104,560,000		144,932,000
60-89 Days Past Due	37,839,000		36,947,000
90 Days or More	594,000		328,000
Total Past Due	142,993,000		182,207,000
Current	12,109,646,000		12,658,949,000
Total loans	12,252,639,000		12,841,156,000
Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	9,768,000		1,850,000
60-89 Days Past Due	1,802,000		690,000
90 Days or More	277,471,000		301,079,000
Total Past Due	289,041,000		303,619,000
Current	67,235,000		11,139,000
Total loans	356,276,000		314,758,000
Consumer and Other Loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	2,193,000		3,223,000
60-89 Days Past Due	894,000		1,315,000
90 Days or More	6,441,000		6,508,000
Total Past Due	9,528,000		11,046,000
Current	244,186,000		253,048,000
Total loans	253,714,000		264,094,000
Allowance for loan losses	(7,605,000)	(6,357,000)	(6,316,000)	(3,457,000)	(3,672,000)	(3,800,000)
Consumer and Other Loans | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	2,193,000		3,223,000
60-89 Days Past Due	894,000		1,315,000
Total Past Due	3,087,000		4,538,000
Current	243,937,000		253,048,000
Total loans	247,024,000		257,586,000
Consumer and Other Loans | Non-accrual loans
Loans receivable and allowance for loan losses
90 Days or More	6,441,000		6,508,000
Total Past Due	6,441,000		6,508,000
Current	249,000
Total loans	6,690,000		6,508,000
Consumer and Other Loans | Home equity lines of credit
Loans receivable and allowance for loan losses
30-59 Days Past Due	2,091,000		3,103,000
60-89 Days Past Due	723,000		1,092,000
90 Days or More	6,410,000		6,459,000
Total Past Due	9,224,000		10,654,000
Current	206,075,000		221,266,000
Total loans	215,299,000		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	2,091,000		3,103,000
60-89 Days Past Due	723,000		1,092,000
Total Past Due	2,814,000		4,195,000
Current	205,840,000		221,266,000
Total loans	208,654,000		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	6,410,000		6,459,000
Total Past Due	6,410,000		6,459,000
Current	235,000
Total loans	6,645,000		6,459,000
Consumer and Other Loans | Other Loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	102,000		120,000
60-89 Days Past Due	171,000		223,000
90 Days or More	31,000		49,000
Total Past Due	304,000		392,000
Current	38,111,000		31,782,000
Total loans	38,415,000		32,174,000
Consumer and Other Loans | Other Loans | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	102,000		120,000
60-89 Days Past Due	171,000		223,000
Total Past Due	273,000		343,000
Current	38,097,000		31,782,000
Total loans	38,370,000		32,125,000
Consumer and Other Loans | Other Loans | Non-accrual loans
Loans receivable and allowance for loan losses
90 Days or More	31,000		49,000
Total Past Due	31,000		49,000
Current	14,000
Total loans	45,000		49,000
Mortgage Loans (Gross)
Loans receivable and allowance for loan losses
30-59 Days Past Due	112,135,000		143,559,000
60-89 Days Past Due	38,747,000		36,322,000
90 Days or More	271,624,000		294,899,000
Total Past Due	422,506,000		474,780,000
Current	11,932,695,000		12,417,040,000
Total loans	12,355,201,000		12,891,820,000
Mortgage Loans (Gross) | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	102,367,000		141,709,000
60-89 Days Past Due	36,945,000		35,632,000
90 Days or More	594,000		328,000
Total Past Due	139,906,000		177,669,000
Current	11,865,709,000		12,405,901,000
Total loans	12,005,615,000		12,583,570,000
Mortgage Loans (Gross) | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	9,768,000		1,850,000
60-89 Days Past Due	1,802,000		690,000
90 Days or More	271,030,000		294,571,000
Total Past Due	282,600,000		297,111,000
Current	66,986,000		11,139,000
Total loans	349,586,000		308,250,000
Mortgage Loans (Gross) | Residential
Loans receivable and allowance for loan losses
30-59 Days Past Due	96,348,000		108,280,000
60-89 Days Past Due	24,445,000		27,814,000
90 Days or More	262,756,000		280,671,000
Total Past Due	383,549,000		416,765,000
Current	8,244,080,000		9,294,461,000
Total loans	8,627,629,000		9,711,226,000
Allowance for loan losses	(78,788,000)	(91,546,000)	(89,267,000)	(87,394,000)	(90,898,000)	(105,991,000)
Mortgage Loans (Gross) | Residential | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	89,746,000		106,430,000
60-89 Days Past Due	22,643,000		27,124,000
Total Past Due	112,389,000		133,554,000
Current	8,180,439,000		9,286,621,000
Total loans	8,292,828,000		9,420,175,000
Mortgage Loans (Gross) | Residential | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	6,602,000		1,850,000
60-89 Days Past Due	1,802,000		690,000
90 Days or More	262,756,000		280,671,000
Total Past Due	271,160,000		283,211,000
Current	63,641,000		7,840,000
Total loans	334,801,000		291,051,000
Mortgage Loans (Gross) | Residential | Full documentation interest-only loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	27,607,000		30,520,000
60-89 Days Past Due	7,652,000		9,650,000
90 Days or More	92,004,000		97,907,000
Total Past Due	127,263,000		138,077,000
Current	1,603,063,000		1,863,319,000
Total loans	1,730,326,000		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	26,078,000		30,520,000
60-89 Days Past Due	7,452,000		8,973,000
Total Past Due	33,530,000		39,493,000
Current	1,580,653,000		1,862,382,000
Total loans	1,614,183,000		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	1,529,000
60-89 Days Past Due	200,000		677,000
90 Days or More	92,004,000		97,907,000
Total Past Due	93,733,000		98,584,000
Current	22,410,000		937,000
Total loans	116,143,000		99,521,000
Mortgage Loans (Gross) | Residential | Full documentation amortizing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	33,445,000		36,281,000
60-89 Days Past Due	4,946,000		6,564,000
90 Days or More	41,604,000		43,014,000
Total Past Due	79,995,000		85,859,000
Current	5,492,246,000		6,219,013,000
Total loans	5,572,241,000		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	31,669,000		35,918,000
60-89 Days Past Due	4,946,000		6,564,000
Total Past Due	36,615,000		42,482,000
Current	5,484,801,000		6,218,064,000
Total loans	5,521,416,000		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	1,776,000		363,000
90 Days or More	41,604,000		43,014,000
Total Past Due	43,380,000		43,377,000
Current	7,445,000		949,000
Total loans	50,825,000		44,326,000
Mortgage Loans (Gross) | Residential | Reduced documentation interest-only loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	24,805,000		29,254,000
60-89 Days Past Due	8,669,000		7,694,000
90 Days or More	102,779,000		107,254,000
Total Past Due	136,253,000		144,202,000
Current	808,632,000		861,093,000
Total loans	944,885,000		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	22,441,000		28,212,000
60-89 Days Past Due	7,673,000		7,694,000
Total Past Due	30,114,000		35,906,000
Current	780,616,000		855,907,000
Total loans	810,730,000		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	2,364,000		1,042,000
60-89 Days Past Due	996,000
90 Days or More	102,779,000		107,254,000
Total Past Due	106,139,000		108,296,000
Current	28,016,000		5,186,000
Total loans	134,155,000		113,482,000
Mortgage Loans (Gross) | Residential | Reduced documentation amortizing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	10,491,000		12,225,000
60-89 Days Past Due	3,178,000		3,906,000
90 Days or More	26,369,000		32,496,000
Total Past Due	40,038,000		48,627,000
Current	340,139,000		351,036,000
Total loans	380,177,000		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	9,558,000		11,780,000
60-89 Days Past Due	2,572,000		3,893,000
Total Past Due	12,130,000		15,673,000
Current	334,369,000		350,268,000
Total loans	346,499,000		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	933,000		445,000
60-89 Days Past Due	606,000		13,000
90 Days or More	26,369,000		32,496,000
Total Past Due	27,908,000		32,954,000
Current	5,770,000		768,000
Total loans	33,678,000		33,722,000
Mortgage Loans (Gross) | Multi-Family
Loans receivable and allowance for loan losses
30-59 Days Past Due	11,597,000		21,743,000
60-89 Days Past Due	10,527,000		5,382,000
90 Days or More	3,311,000		7,359,000
Total Past Due	25,435,000		34,484,000
Current	2,872,057,000		2,372,194,000
Total loans	2,897,492,000		2,406,678,000
Allowance for loan losses	(40,865,000)	(33,952,000)	(35,514,000)	(48,142,000)	(44,927,000)	(35,422,000)
Mortgage Loans (Gross) | Multi-Family | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	11,232,000		21,743,000
60-89 Days Past Due	10,527,000		5,382,000
Total Past Due	21,759,000		27,125,000
Current	2,871,071,000		2,368,895,000
Total loans	2,892,830,000		2,396,020,000
Mortgage Loans (Gross) | Multi-Family | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	365,000
90 Days or More	3,311,000		7,359,000
Total Past Due	3,676,000		7,359,000
Current	986,000		3,299,000
Total loans	4,662,000		10,658,000
Mortgage Loans (Gross) | Commercial Real Estate
Loans receivable and allowance for loan losses
30-59 Days Past Due	4,190,000		13,536,000
60-89 Days Past Due	3,775,000		3,126,000
90 Days or More	5,557,000		6,869,000
Total Past Due	13,522,000		23,531,000
Current	816,558,000		750,385,000
Total loans	830,080,000		773,916,000
Allowance for loan losses	(16,642,000)	(12,395,000)	(14,404,000)	(9,109,000)	(10,402,000)	(11,972,000)
Mortgage Loans (Gross) | Commercial Real Estate | Accruing loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	1,389,000		13,536,000
60-89 Days Past Due	3,775,000		3,126,000
90 Days or More	594,000		328,000
Total Past Due	5,758,000		16,990,000
Current	814,199,000		750,385,000
Total loans	819,957,000		767,375,000
Mortgage Loans (Gross) | Commercial Real Estate | Non-accrual loans
Loans receivable and allowance for loan losses
30-59 Days Past Due	2,801,000
90 Days or More	4,963,000		6,541,000
Total Past Due	7,764,000		6,541,000
Current	2,359,000
Total loans	$ 10,123,000		$ 6,541,000