Fair Value Measurements - Recurring Assets (Details) - Available-for-sale Securities - Recurring - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Mortgage-backed securities
Fair Value Measurements
Total assets	$ 5,072	$ 9,313
Asset-backed securities
Fair Value Measurements
Total assets	56	109
State and political securities
Fair Value Measurements
Total assets	65,330	60,934
Other debt securities
Fair Value Measurements
Total assets	55,303	51,118
Financial institution equity securities
Fair Value Measurements
Total assets	9,898	10,535
Non-financial institution equity securities
Fair Value Measurements
Total assets	1,251	1,483
Level I | Mortgage-backed securities
Fair Value Measurements
Total assets	0	0
Level I | Asset-backed securities
Fair Value Measurements
Total assets	0	0
Level I | State and political securities
Fair Value Measurements
Total assets	0	0
Level I | Other debt securities
Fair Value Measurements
Total assets	0	0
Level I | Financial institution equity securities
Fair Value Measurements
Total assets	9,898	10,535
Level I | Non-financial institution equity securities
Fair Value Measurements
Total assets	1,251	1,483
Level II | Mortgage-backed securities
Fair Value Measurements
Total assets	5,072	9,313
Level II | Asset-backed securities
Fair Value Measurements
Total assets	56	109
Level II | State and political securities
Fair Value Measurements
Total assets	65,330	60,934
Level II | Other debt securities
Fair Value Measurements
Total assets	55,303	51,118
Level II | Financial institution equity securities
Fair Value Measurements
Total assets	0	0
Level II | Non-financial institution equity securities
Fair Value Measurements
Total assets	0	0
Level III | Mortgage-backed securities
Fair Value Measurements
Total assets	0	0
Level III | Asset-backed securities
Fair Value Measurements
Total assets	0	0
Level III | State and political securities
Fair Value Measurements
Total assets	0	0
Level III | Other debt securities
Fair Value Measurements
Total assets	0	0
Level III | Financial institution equity securities
Fair Value Measurements
Total assets	0	0
Level III | Non-financial institution equity securities
Fair Value Measurements
Total assets	$ 0	$ 0