Loans - Investment Of Originated Loans Held-For-Investment, Net Of Deferred Fees And Costs, By Loan Type And Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	$ 2,144,346	$ 1,931,585
Pass
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	2,108,992	1,888,301
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	9,943	8,718
Substandard
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	25,411	34,566
Multifamily | Real Estate Loans | Less Than 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	122,590	125,504
Multifamily | Real Estate Loans | Greater Than or Equal to 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	1,387,510	1,195,220
Multifamily | Real Estate Loans | Pass | Less Than 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	122,525	124,678
Multifamily | Real Estate Loans | Pass | Greater Than or Equal to 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	1,381,231	1,188,916
Multifamily | Real Estate Loans | Special Mention | Less Than 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	25	51
Multifamily | Real Estate Loans | Special Mention | Greater Than or Equal to 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	4,636	3,832
Multifamily | Real Estate Loans | Substandard | Less Than 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	40	775
Multifamily | Real Estate Loans | Substandard | Greater Than or Equal to 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	1,643	2,472
Commercial mortgage | Real Estate Loans | Less Than 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	66,791	54,460
Commercial mortgage | Real Estate Loans | Greater Than or Equal to 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	346,561	348,254
Commercial mortgage | Real Estate Loans | Pass | Less Than 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	65,612	52,253
Commercial mortgage | Real Estate Loans | Pass | Greater Than or Equal to 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	323,842	319,733
Commercial mortgage | Real Estate Loans | Special Mention | Less Than 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	0	974
Commercial mortgage | Real Estate Loans | Special Mention | Greater Than or Equal to 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	3,852	2,966
Commercial mortgage | Real Estate Loans | Substandard | Less Than 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	1,179	1,233
Commercial mortgage | Real Estate Loans | Substandard | Greater Than or Equal to 35% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	18,867	25,555
One-to-four family residential mortgage | Real Estate Loans | Less Than 60% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	61,726	51,045
One-to-four family residential mortgage | Real Estate Loans | Greater than or Equal to 60% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	44,798	47,965
One-to-four family residential mortgage | Real Estate Loans | Pass | Less Than 60% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	59,214	48,429
One-to-four family residential mortgage | Real Estate Loans | Pass | Greater than or Equal to 60% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	43,316	46,578
One-to-four family residential mortgage | Real Estate Loans | Special Mention | Less Than 60% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	705	504
One-to-four family residential mortgage | Real Estate Loans | Special Mention | Greater than or Equal to 60% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	0	0
One-to-four family residential mortgage | Real Estate Loans | Substandard | Less Than 60% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	1,807	2,112
One-to-four family residential mortgage | Real Estate Loans | Substandard | Greater than or Equal to 60% LTV
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	1,482	1,387
Construction and land | Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	14,092	18,677
Construction and land | Real Estate Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	14,092	18,677
Construction and land | Real Estate Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	0	0
Construction and land | Real Estate Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	0	0
Home equity and lines of credit | Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	66,767	62,594
Home equity and lines of credit | Real Estate Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	66,489	61,935
Home equity and lines of credit | Real Estate Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	29	75
Home equity and lines of credit | Real Estate Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	249	584
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	32,013	25,610
Commercial and Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	31,173	24,846
Commercial and Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	696	316
Commercial and Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	144	448
Other loans
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	1,498	2,256
Other loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	1,498	2,256
Other loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	0	0
Other loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Originated loans held-for-investment, net	$ 0	$ 0