Employee Benefits (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended			120 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution amounts	$ 2,500	$ 2,300	$ 2,300
Other incentive-based compensation expense	16,100	16,900	$ 16,000
Deferred compensation plan, accrued liability	$ 15,700	14,200
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	$ 12,800	6,641
Accumulated benefit obligation	67,400	72,900
Estimated amortization of prior service cost (credit) from accumulated other comprehensive loss into net period benefit cost, next year	(16)
Estimated amortization of (gain) loss from accumulated other comprehensive loss into net period benefit cost, next year	$ 792
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	$ (14,626)	(15,203)
Available-for-sale securities and other short-term investments, rabbi trusts	14,600	13,300
Accumulated benefit obligation	13,200	$ 14,000
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	408
Estimated future employer contributions in next fiscal year	$ 907
Non-elective Employer Contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution	4.00%
Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Transition Period Pension Plan Amendment				10 years