Employee Benefits (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended			120 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution amounts	$ 2,700	$ 2,500	$ 2,300
Other incentive-based compensation expense	16,700	16,100	$ 16,900
Deferred compensation plan, accrued liability	$ 17,900	15,700
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	$ 10,608	12,800
Accumulated benefit obligation	76,600	67,400
Estimated amortization of prior service cost (credit) from accumulated other comprehensive loss into net period benefit cost, next year	0
Estimated amortization of (gain) loss from accumulated other comprehensive loss into net period benefit cost, next year	$ 1,600
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	$ (16,438)	(14,626)
Available-for-sale securities and other short-term investments, rabbi trusts	14,300	14,600
Accumulated benefit obligation	14,900	$ 13,200
Estimated amortization of prior service cost (credit) from accumulated other comprehensive loss into net period benefit cost, next year	0
Estimated amortization of (gain) loss from accumulated other comprehensive loss into net period benefit cost, next year	559
Estimated future employer contributions in next fiscal year	$ 898
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 years