Employee Benefit Plans (Schedule of Defined Benefit Plans Disclosures) (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]
Service cost	$ 6,677	$ 7,440	$ 6,320
Interest cost	4,922	4,365	4,651
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	212,506
Value of Plan Assets at end of year	211,802	212,506
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	228,873	270,098
Service cost	0	0	0
Interest cost	8,141	9,269	11,169
Settlement gain	(1,326)	(2,332)
Curtailments	0	0
Benefits paid	(34,918)	(36,895)
Other-primarily actuarial (gain) loss	16,778	(11,267)
Benefit Obligations at end of year	217,548	228,873	270,098
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	212,506	255,642
Actual return on plan assets	33,998	(6,463)
Employer contributions	216	222
Benefits paid	(34,918)	(36,895)
Value of Plan Assets at end of year	211,802	212,506	255,642
Accrued benefit cost	(5,746)	(16,367)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit	992	0
Accumulated gain	14,537	8,899
Total not yet recognized as a component of net periodic benefit cost	15,529	8,899
BALANCE SHEET AMOUNTS
Current liability	(270)	(220)
Noncurrent liability	(5,476)	(16,147)
Liability, Defined Benefit Plan	(5,746)	(16,367)
Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	88,563	110,519
Service cost	480	558	671
Interest cost	3,505	3,674	4,150
Settlement gain	0	0
Curtailments	30	0
Benefits paid	(7,304)	(5,388)
Other-primarily actuarial (gain) loss	2,593	(20,800)
Benefit Obligations at end of year	87,867	88,563	110,519
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	0	0
Actual return on plan assets		0
Employer contributions	7,304	5,388
Benefits paid	(7,304)	(5,388)
Value of Plan Assets at end of year	0	0	$ 0
Accrued benefit cost	(87,867)	(88,563)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit	0	0
Accumulated gain	20,333	25,936
Total not yet recognized as a component of net periodic benefit cost	20,333	25,936
BALANCE SHEET AMOUNTS
Current liability	(7,300)	(5,400)
Noncurrent liability	(80,567)	(83,163)
Liability, Defined Benefit Plan	$ (87,867)	$ (88,563)