Benefit Plans - Fair Value Measurement of Plan Assets (Details) - Pension Plan - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Benefit Plans
Fair value of plan assets	$ 106,648,000	$ 114,795,000	$ 112,659,000
Percentage of total	100.00%	100.00%
Minimum
Benefit Plans
Percentage of assets in high-grade corporate bonds and U.S. government debt obligations	80.00%
Cash and cash equivalents
Benefit Plans
Fair value of plan assets	$ 4,451,000	$ 2,576,000
Fixed income securities
Benefit Plans
Percentage of total	84.60%	85.10%
U.S. Treasury securities
Benefit Plans
Fair value of plan assets	$ 8,343,000	$ 6,776,000
Government agency debt securities
Benefit Plans
Fair value of plan assets	9,674,000	12,441,000
Fixed income - U.S. corporate securities
Benefit Plans
Fair value of plan assets	69,926,000	70,401,000
Fixed income - municipal securities
Benefit Plans
Fair value of plan assets	495,000	521,000
Fixed income - mutual funds
Benefit Plans
Fair value of plan assets		5,626,000
Fixed income - international securities
Benefit Plans
Fair value of plan assets	1,779,000	1,980,000
Equity - large-cap exchange-traded fund
Benefit Plans
Fair value of plan assets	7,840,000	9,321,000
Equity - mid-cap exchange-traded funds
Benefit Plans
Fair value of plan assets	1,360,000	1,566,000
Equity - small-cap exchange-traded funds
Benefit Plans
Fair value of plan assets	654,000	785,000
Equity - international funds
Benefit Plans
Fair value of plan assets	2,126,000	2,802,000
Level 1
Benefit Plans
Fair value of plan assets	18,210,000	24,656,000
Level 1 | Cash and cash equivalents
Benefit Plans
Fair value of plan assets	4,451,000	2,576,000
Level 1 | Fixed income - mutual funds
Benefit Plans
Fair value of plan assets		5,626,000
Level 1 | Fixed income - international securities
Benefit Plans
Fair value of plan assets	1,779,000	1,980,000
Level 1 | Equity - large-cap exchange-traded fund
Benefit Plans
Fair value of plan assets	7,840,000	9,321,000
Level 1 | Equity - mid-cap exchange-traded funds
Benefit Plans
Fair value of plan assets	1,360,000	1,566,000
Level 1 | Equity - small-cap exchange-traded funds
Benefit Plans
Fair value of plan assets	654,000	785,000
Level 1 | Equity - international funds
Benefit Plans
Fair value of plan assets	2,126,000	2,802,000
Level 2
Benefit Plans
Fair value of plan assets	88,438,000	90,139,000
Level 2 | U.S. Treasury securities
Benefit Plans
Fair value of plan assets	8,343,000	6,776,000
Level 2 | Government agency debt securities
Benefit Plans
Fair value of plan assets	9,674,000	12,441,000
Level 2 | Fixed income - U.S. corporate securities
Benefit Plans
Fair value of plan assets	69,926,000	70,401,000
Level 2 | Fixed income - municipal securities
Benefit Plans
Fair value of plan assets	495,000	521,000
Level 3
Benefit Plans
Fair value of plan assets	$ 0	$ 0