Securities, Held-to-maturity Securities (Details) $ in Thousands	Sep. 30, 2018 USD ($) security	Dec. 31, 2017 USD ($) security
Amortized cost and fair value of investment securities held to maturity [Abstract]
Amortized Cost	$ 43,108	$ 54,303
Unrealized Gains	32	176
Unrealized Losses	1,274	475
Fair Value	41,866	54,004
Fair Value [Abstract]
Less than 12 Months, Fair Value	6,627	29,963
12 Months or More, Fair Value	29,999	14,010
Total, Estimated Fair Value	36,626	43,973
Unrealized Losses [Abstract]
Less than 12 Months, Unrealized Losses	121	246
12 Months or More, Unrealized Losses	1,153	229
Total, Unrealized Losses	1,274	475
U.S. Treasury Securities [Member]
Amortized cost and fair value of investment securities held to maturity [Abstract]
Amortized Cost	3,991	4,994
Unrealized Gains	14	68
Unrealized Losses	2	6
Fair Value	4,003	5,056
Fair Value [Abstract]
Less than 12 Months, Fair Value		1,993
12 Months or More, Fair Value	998
Total, Estimated Fair Value	998	1,993
Unrealized Losses [Abstract]
Less than 12 Months, Unrealized Losses		6
12 Months or More, Unrealized Losses	2
Total, Unrealized Losses	$ 2	$ 6
HTM securities - Number of securities in continuous unrealized loss position | security	1	1
U.S. Government Agency Notes [Member]
Amortized cost and fair value of investment securities held to maturity [Abstract]
Amortized Cost	$ 12,993	$ 19,004
Unrealized Gains	10	81
Unrealized Losses	133	99
Fair Value	12,870	18,986
Fair Value [Abstract]
Less than 12 Months, Fair Value	2,978	6,977
12 Months or More, Fair Value	7,911	6,964
Total, Estimated Fair Value	10,889	13,941
Unrealized Losses [Abstract]
Less than 12 Months, Unrealized Losses	15	23
12 Months or More, Unrealized Losses	118	76
Total, Unrealized Losses	$ 133	$ 99
HTM securities - Number of securities in continuous unrealized loss position | security	11	14
Mortgage-backed Securities [Member]
Amortized cost and fair value of investment securities held to maturity [Abstract]
Amortized Cost	$ 26,124	$ 30,305
Unrealized Gains	8	27
Unrealized Losses	1,139	370
Fair Value	24,993	29,962
Fair Value [Abstract]
Less than 12 Months, Fair Value	3,649	20,993
12 Months or More, Fair Value	21,090	7,046
Total, Estimated Fair Value	24,739	28,039
Unrealized Losses [Abstract]
Less than 12 Months, Unrealized Losses	106	217
12 Months or More, Unrealized Losses	1,033	153
Total, Unrealized Losses	$ 1,139	$ 370
HTM securities - Number of securities in continuous unrealized loss position | security	18	16