Qualified Employee Benefit Plans - Reconciliation of Amounts Recognized in Other Comprehensive Income for the Retirement Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	$ (7,891)	$ 1,586	$ (3,190)
Amortization of prior service cost	24	24	24
Changes in employee benefit related items	7,867	(1,610)	3,166
Income tax benefit (expense)	274	(139)	(27)
Other comprehensive (loss) income	(7,593)
Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	(7,934)
Amortization of prior service cost	24	24	24
Changes in employee benefit related items	7,910	(1,894)	3,019
Income tax benefit (expense)	312
Other comprehensive (loss) income	(7,598)	$ 1,687	$ (3,068)
Retired Individual Plan
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	(69)
Amortization of prior service cost	0
Changes in employee benefit related items	69
Income tax benefit (expense)	3
Other comprehensive (loss) income	(66)
Foreign Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	112
Amortization of prior service cost	0
Changes in employee benefit related items	(112)
Income tax benefit (expense)	(41)
Other comprehensive (loss) income	$ 71