Loans Receivable and Allowance for Loan Losses (Details 8) (USD $)	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans individually evaluated for impairment	$ 393,677,000		$ 346,906,000
Loans collectively evaluated for impairment	12,215,238,000		12,809,008,000
Total loans	12,608,915,000		13,155,914,000
Loans individually evaluated for impairment, allowance for loan losses	21,033,000		5,046,000
Loans collectively evaluated for impairment, allowance for loan losses	122,867,000		140,455,000
Total allowance for loan losses	143,900,000	144,250,000	145,501,000	148,102,000	149,899,000	157,185,000
Consumer and Other Loans
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans collectively evaluated for impairment	253,714,000		264,094,000
Total loans	253,714,000		264,094,000
Loans collectively evaluated for impairment, allowance for loan losses	7,605,000		6,316,000
Total allowance for loan losses	7,605,000	6,357,000	6,316,000	3,457,000	3,672,000	3,800,000
Mortgage Loans (Gross)
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Total loans	12,355,201,000		12,891,820,000
Mortgage Loans (Gross) | Residential
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans individually evaluated for impairment	326,469,000		272,146,000
Loans collectively evaluated for impairment	8,301,160,000		9,439,080,000
Total loans	8,627,629,000		9,711,226,000
Loans individually evaluated for impairment, allowance for loan losses	19,045,000		1,001,000
Loans collectively evaluated for impairment, allowance for loan losses	59,743,000		88,266,000
Total 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) | Multi-Family
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans individually evaluated for impairment	46,651,000		56,116,000
Loans collectively evaluated for impairment	2,850,841,000		2,350,562,000
Total loans	2,897,492,000		2,406,678,000
Loans individually evaluated for impairment, allowance for loan losses	1,194,000		2,576,000
Loans collectively evaluated for impairment, allowance for loan losses	39,671,000		32,938,000
Total 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) | Commercial Real Estate
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans individually evaluated for impairment	20,557,000		18,644,000
Loans collectively evaluated for impairment	809,523,000		755,272,000
Total loans	830,080,000		773,916,000
Loans individually evaluated for impairment, allowance for loan losses	794,000		1,469,000
Loans collectively evaluated for impairment, allowance for loan losses	15,848,000		12,935,000
Total allowance for loan losses	$ 16,642,000	$ 12,395,000	$ 14,404,000	$ 9,109,000	$ 10,402,000	$ 11,972,000