Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0	$ 3,300
Defined contribution plan, cost recognized	$ 8,600	10,700	$ 9,800
Salary continuation plan minimum period	10 years
Salary continuation plan maximum period	20 years
Present value of future salary contribution plan benefits	$ 28,700	27,300
Postemployment benefits, period expense	1,500	1,000	$ 2,200
Deferred compensation cash-based arrangements, liability, current and noncurrent	12,200	11,000
Cash surrender value of life insurance	320,600	313,600
Other postretirement defined benefit plan, liabilities	3,400	6,800
Supplemental Employee Retirement Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other deferred compensation arrangements, liability, current and noncurrent	$ 529	475,000
Percentage of deferred salary	50.00%
Deferred compensation liability, current and noncurrent	$ 9,700	8,600
Pension and other postretirement defined benefit plans, liabilities	$ 9,000	$ 9,400