Loans Receivable and Allowance for Credit Losses (Impact of ASC 326 Adoption) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses	$ 86,259	$ 75,143	$ 55,525	$ 55,525	$ 62,810	$ 55,353	$ 55,562
Mortgage Portfolio
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			25,551
Mortgage Portfolio | Residential
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			3,411
Mortgage Portfolio | Commercial
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			12,885
Mortgage Portfolio | Multifamily
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			3,370
Mortgage Portfolio | Construction
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			5,885
Commercial Loans
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses	25,284	22,841	28,228	28,263	33,549	26,351	25,693
Consumer Loans
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses	$ 6,104	$ 4,802	1,746	$ 1,751	$ 1,981	$ 2,076	$ 2,191
Cumulative Effect, Period of Adoption, Adjusted Balance
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			63,445
Cumulative Effect, Period of Adoption, Adjusted Balance | Mortgage Portfolio
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			39,739
Cumulative Effect, Period of Adoption, Adjusted Balance | Mortgage Portfolio | Residential
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			8,950
Cumulative Effect, Period of Adoption, Adjusted Balance | Mortgage Portfolio | Commercial
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			17,118
Cumulative Effect, Period of Adoption, Adjusted Balance | Mortgage Portfolio | Multifamily
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			9,519
Cumulative Effect, Period of Adoption, Adjusted Balance | Mortgage Portfolio | Construction
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			4,152
Cumulative Effect, Period of Adoption, Adjusted Balance | Commercial Loans
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			18,254
Cumulative Effect, Period of Adoption, Adjusted Balance | Consumer Loans
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			5,452
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			7,920
Cumulative Effect, Period of Adoption, Adjustment | Mortgage Portfolio
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			14,188
Cumulative Effect, Period of Adoption, Adjustment | Mortgage Portfolio | Residential
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			5,539
Cumulative Effect, Period of Adoption, Adjustment | Mortgage Portfolio | Commercial
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			4,233
Cumulative Effect, Period of Adoption, Adjustment | Mortgage Portfolio | Multifamily
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			6,149
Cumulative Effect, Period of Adoption, Adjustment | Mortgage Portfolio | Construction
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			(1,733)
Cumulative Effect, Period of Adoption, Adjustment | Commercial Loans
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			(9,974)
Cumulative Effect, Period of Adoption, Adjustment | Consumer Loans
New Accounting Pronouncement, Early Adoption [Line Items]
Allowance for credit losses			$ 3,706