Employee Benefits (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended			120 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution amounts	$ 2,800	$ 2,700	$ 2,500
Deferred compensation plan, accrued liability	$ 19,400	17,900
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution	3.00%
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded (unfunded) status at end of period	$ 7,187	10,608
Accumulated benefit obligation	$ 87,900	76,600
Fair value of equity securities, maximum percentage held by a single issuer	10.00%
Non-Qualified Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded (unfunded) status at end of period	$ (17,973)	(16,438)
Available-for-sale securities and other short-term investments, rabbi trusts	13,700	14,300
Accumulated benefit obligation	16,400	$ 14,900
Estimated future employer contributions in next fiscal year	$ 896
Non-elective Employer Contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution	4.00%
Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Transition Period Pension Plan Amendment				10