Fair Value - Annual Fair Value Measurements of Pension Plan Asses (Details) - USD ($) $ in Thousands		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		$ 92,290	[1]	$ 76,210	$ 66,159
Mutual funds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	[2]	34,231		27,246
U.S. agency securities
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		7,405		8,015
Corporate debt securities
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		10,865		10,472
Common stocks
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		34,693		26,882
Common trust fund
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		5,096		3,595
Level 1
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		72,644		58,517
Level 1 | Mutual funds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	[2]	34,231		27,246
Level 1 | U.S. agency securities
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		3,720		4,389
Level 1 | Corporate debt securities
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0		0
Level 1 | Common stocks
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		34,693		26,882
Level 2
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		14,550		14,098
Level 2 | Mutual funds
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	[2]	0		0
Level 2 | U.S. agency securities
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		3,685		3,626
Level 2 | Corporate debt securities
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		10,865		10,472
Level 2 | Common stocks
Fair Value Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		$ 0		$ 0

[1] Additional information regarding the fair value of Pension Plan assets as of December 31, 2019 can be found in Note 22, "Fair Value."

[2] Includes mutual funds, money market funds, cash, cash equivalents, and accrued interest.