Employee Benefit Plans (Schedule of Defined Benefit Plan Activity) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Amounts recognized in the consolidated balance sheets:
Prepaid pension costs	$ 35,209	$ 31,686
Non-current employee benefit liabilities	(66,616)	(67,853)
Pension Benefits
Change in benefit obligation:
Benefit obligation at January 1	(128,997)	(123,165)
Service cost	(592)	(533)	$ (587)
Interest cost	(3,545)	(4,860)	(4,495)
Plan settlement	7,255	0
Benefits paid	7,008	7,696
Expenses paid	255	391
Actuarial loss	(7,226)	(8,526)
Benefit obligation at December 31	(125,842)	(128,997)	(123,165)
Change in plan assets:
Fair value of plan assets at January 1	101,051	93,167
Actual return on plan assets	8,919	15,788
Plan settlement	(7,255)	0
Expenses paid	(255)	(391)
Contributions	7,360	183
Benefits paid	(7,008)	(7,696)
Fair value of plan assets at December 31	102,812	101,051	93,167
Unfunded status at December 31	(23,030)	(27,946)
Amounts recognized in the consolidated balance sheets:
Prepaid pension costs	35,209	31,686
Other accrued liabilities	(100)	(111)
Non-current employee benefit liabilities	(58,139)	(59,521)
Net amounts recognized	(23,030)	(27,946)
Other Postretirement Benefits
Change in benefit obligation:
Benefit obligation at January 1	(8,986)	(8,296)
Service cost	0	(3)	(4)
Interest cost	(286)	(347)	(330)
Plan settlement	0	0
Benefits paid	500	594
Expenses paid	0	0
Actuarial loss	(329)	(934)
Benefit obligation at December 31	(9,101)	(8,986)	(8,296)
Change in plan assets:
Fair value of plan assets at January 1	0	0
Actual return on plan assets	0	0
Plan settlement	0	0
Expenses paid	0	0
Contributions	500	594
Benefits paid	(500)	(594)
Fair value of plan assets at December 31	0	0	$ 0
Unfunded status at December 31	(9,101)	(8,986)
Amounts recognized in the consolidated balance sheets:
Prepaid pension costs	0	0
Other accrued liabilities	(624)	(654)
Non-current employee benefit liabilities	(8,477)	(8,332)
Net amounts recognized	$ (9,101)	$ (8,986)