Pension Plans (Obligations and Funded Status) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Fair value of plan assets at beginning of year		$ 643,392
Fair value of plan assets at end of year		590,387		$ 643,392
Noncurrent liabilities		(104,988)		(126,924)
Qualified Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year		770,316		728,601
Service cost		4,897		4,794	$ 4,596
Interest cost		23,804		24,358	24,488
Actuarial liability (gain) loss (1)	[1]	(67,157)		47,433
Benefit payments		36,485		34,870
Projected benefit obligation at end of year		695,375		770,316	728,601
Fair value of plan assets at beginning of year		643,392		572,174
Actual return on plan assets		(46,520)		96,088
Employer contributions		30,000		10,000
Fair value of plan assets at end of year		590,387		643,392	572,174
Funded status at end of year		(104,988)		(126,924)
Accumulated benefit obligation		695,375		770,316
Current liabilities		0	[2]	0
Noncurrent liabilities		(104,988)		(126,924)
Total		(104,988)		(126,924)
Unrecognized loss		189,047		173,214
Amount included in accumulated other comprehensive income		189,047		173,214
Expected amortization defined benefit plan		14,300
SERP
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year		7,896		10,059
Service cost		0		0	0
Interest cost		246		241	254
Actuarial liability (gain) loss (1)	[1]	(280)		652
Benefit payments		949		3,056
Projected benefit obligation at end of year		6,913		7,896	10,059
Fair value of plan assets at beginning of year		0		0
Actual return on plan assets		0		0
Employer contributions		949		3,056
Fair value of plan assets at end of year		0		0	$ 0
Funded status at end of year		(6,913)		(7,896)
Accumulated benefit obligation		6,913		7,896
Current liabilities		(529)		(942)
Noncurrent liabilities		(6,384)		(6,954)
Total		(6,913)		(7,896)
Unrecognized loss		837		1,410
Amount included in accumulated other comprehensive income		837		$ 1,410
Expected amortization defined benefit plan		$ 200

[1] The actuarial liability (gain) loss amount for the qualified pension plan for 2018 and 2017 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