Pension Plans (Obligations and Funded Status) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Fair value of plan assets at beginning of year		$ 590,387
Fair value of plan assets at end of year		680,142		$ 590,387
Noncurrent liabilities		(97,246)		(104,988)
Qualified Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year		695,375		770,316
Service cost		5,100		4,897	$ 4,794
Interest cost		26,422		23,804	24,358
Actuarial liability loss (gain) (1)	[1]	88,271		(67,157)
Benefit payments		37,780		36,485
Projected benefit obligation at end of year		777,388		695,375	770,316
Fair value of plan assets at beginning of year		590,387		643,392
Actual return on plan assets		127,535		(46,520)
Employer contributions		0		30,000
Fair value of plan assets at end of year		680,142		590,387	643,392
Funded status at end of year		(97,246)		(104,988)
Accumulated benefit obligation		777,388		695,375
Current liabilities		0	[2]	0
Noncurrent liabilities		(97,246)		(104,988)
Total		(97,246)		(104,988)
Unrecognized loss		177,083		189,047
Amount included in accumulated other comprehensive income		177,083		189,047
Expected amortization defined benefit plan		4,600
SERP
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year		6,913		7,896
Service cost		0		0	0
Interest cost		237		246	241
Actuarial liability loss (gain) (1)	[1]	720		(280)
Benefit payments		534		949
Projected benefit obligation at end of year		7,336		6,913	7,896
Fair value of plan assets at beginning of year		0		0
Actual return on plan assets		0		0
Employer contributions		534		949
Fair value of plan assets at end of year		0		0	$ 0
Funded status at end of year		(7,336)		(6,913)
Accumulated benefit obligation		7,336		6,913
Current liabilities		(528)		(529)
Noncurrent liabilities		(6,808)		(6,384)
Total		(7,336)		(6,913)
Unrecognized loss		1,311		837
Amount included in accumulated other comprehensive income		1,311		$ 837
Expected amortization defined benefit plan		$ 900

[1] The actuarial liability loss (gain) amount for the qualified pension plan for 2019 and 2018 is principally due to the effect of changes in the discount rate.

[2] ⁽¹⁾ The current liabilities are included in other current liabilities on the Consolidated Balance Sheets