Loans Receivable - Mortgage Banking Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Loans held for sale	$ 1,555	$ 2,288
One-to-four family residential
One-to-four family residential loans:
Originated	121,998	144,066	$ 178,169
Sold	76,834	113,786	141,127
Gains on sales of loans, net	2,403	3,412	$ 3,723
Contractual amounts of commitments to sell and fund with off-balance sheet risk:
Commitments to sell mortgage loans	3,910	10,140
Commitments to fund mortgage loans (at interest rates approximating market rates) for portfolio or for sale:
Fixed rate	6,593	10,894
Variable or adjustable rate	1,008	56
Total commitments to fund mortgage loans	$ 7,601	$ 10,950