Fair Value Measurements (Carrying Values of Assets Measured at Estimated Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value of Financial Instruments
Total securities available-for-sale	$ 388,878	$ 416,798
Total residential mortgage-backed securities
Fair Value of Financial Instruments
Total securities available-for-sale	315,148	344,857
GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	301,787	330,539
Non-GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	2,617	3,054
GSE pass-through certificates
Fair Value of Financial Instruments
Total securities available-for-sale	10,744	11,264
Obligations of GSEs
Fair Value of Financial Instruments
Total securities available-for-sale	73,729	71,939
Fannie Mae stock
Fair Value of Financial Instruments
Total securities available-for-sale	1	2
Recurring basis
Fair Value of Financial Instruments
Total securities available-for-sale	388,878	416,798
Recurring basis | GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	301,787	330,539
Recurring basis | Non-GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	2,617	3,054
Recurring basis | GSE pass-through certificates
Fair Value of Financial Instruments
Total securities available-for-sale	10,744	11,264
Recurring basis | Obligations of GSEs
Fair Value of Financial Instruments
Total securities available-for-sale	73,729	71,939
Recurring basis | Fannie Mae stock
Fair Value of Financial Instruments
Total securities available-for-sale	1	2
Recurring basis | Level 1
Fair Value of Financial Instruments
Total securities available-for-sale	1	2
Recurring basis | Level 1 | GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	0	0
Recurring basis | Level 1 | Non-GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	0	0
Recurring basis | Level 1 | GSE pass-through certificates
Fair Value of Financial Instruments
Total securities available-for-sale	0	0
Recurring basis | Level 1 | Obligations of GSEs
Fair Value of Financial Instruments
Total securities available-for-sale	0	0
Recurring basis | Level 1 | Fannie Mae stock
Fair Value of Financial Instruments
Total securities available-for-sale	1	2
Recurring basis | Level 2
Fair Value of Financial Instruments
Total securities available-for-sale	388,877	416,796
Recurring basis | Level 2 | GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	301,787	330,539
Recurring basis | Level 2 | Non-GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	2,617	3,054
Recurring basis | Level 2 | GSE pass-through certificates
Fair Value of Financial Instruments
Total securities available-for-sale	10,744	11,264
Recurring basis | Level 2 | Obligations of GSEs
Fair Value of Financial Instruments
Total securities available-for-sale	73,729	71,939
Recurring basis | Level 2 | Fannie Mae stock
Fair Value of Financial Instruments
Total securities available-for-sale	$ 0	$ 0