Loans Receivable and Allowance for Loan Losses (Summary of Loans Receivable by Credit Quality Risk Rating Indicator) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	$ 7,294,205	$ 7,328,963
Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	137,034	110,563
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	38,231	44,736
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	98,375	65,399
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	428	428
Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Acceptable/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	7,157,171	7,218,400
Mortgage Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	5,107,684	5,109,868
Total gross loans	5,107,684	5,109,868
Mortgage Portfolio Segment [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	54,542	56,686
Mortgage Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	23,379	23,512
Mortgage Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	31,163	33,174
Mortgage Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Acceptable/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	5,053,142	5,053,182
Mortgage Portfolio Segment [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	1,127,744	1,142,347
Total gross loans	1,127,744	1,142,347
Mortgage Portfolio Segment [Member] | Residential Real Estate [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	15,037	12,430
Mortgage Portfolio Segment [Member] | Residential Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	6,694	4,325
Mortgage Portfolio Segment [Member] | Residential Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	8,343	8,105
Mortgage Portfolio Segment [Member] | Residential Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Residential Real Estate [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Residential Real Estate [Member] | Acceptable/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	1,112,707	1,129,917
Mortgage Portfolio Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	2,185,107	2,171,056
Total gross loans	2,185,107	2,171,056
Mortgage Portfolio Segment [Member] | Commercial Real Estate [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	38,916	44,241
Mortgage Portfolio Segment [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	16,334	19,172
Mortgage Portfolio Segment [Member] | Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	22,582	25,069
Mortgage Portfolio Segment [Member] | Commercial Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Commercial Real Estate [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Commercial Real Estate [Member] | Acceptable/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	2,146,191	2,126,815
Mortgage Portfolio Segment [Member] | Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	1,423,834	1,403,885
Total gross loans	1,423,834	1,403,885
Mortgage Portfolio Segment [Member] | Multifamily [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	589	15
Mortgage Portfolio Segment [Member] | Multifamily [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	351	15
Mortgage Portfolio Segment [Member] | Multifamily [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	238	0
Mortgage Portfolio Segment [Member] | Multifamily [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Multifamily [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Multifamily [Member] | Acceptable/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	1,423,245	1,403,870
Mortgage Portfolio Segment [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	370,999	392,580
Total gross loans	370,999	392,580
Mortgage Portfolio Segment [Member] | Construction [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Construction [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Construction [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Construction [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Construction [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	0	0
Mortgage Portfolio Segment [Member] | Construction [Member] | Acceptable/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Mortgage loan	370,999	392,580
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,725,780	1,745,138
Commercial Loans [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	79,873	50,900
Commercial Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	14,204	20,738
Commercial Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	65,241	29,734
Commercial Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	428	428
Commercial Loans [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Commercial Loans [Member] | Acceptable/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,645,907	1,694,238
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	460,741	473,957
Consumer Loans [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,619	2,977
Consumer Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	648	486
Consumer Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,971	2,491
Consumer Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer Loans [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer Loans [Member] | Acceptable/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	$ 458,122	$ 470,980