Employee Benefit Plans (Schedule of Defined Benefit Plans Disclosures) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 1,583	$ 7,440	$ 6,320
Interest cost	1,126	4,365	4,651
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year		172,502
Value of Plan Assets at end of year		134,986	172,502
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year		270,098	313,629
Service cost	0	0	0
Interest cost	2,768	9,269	11,169
Divestitures (see Note 5 to the Consolidated Financial Statements)		0	(29,097)
Settlement gain		(2,332)	(1,532)
Curtailments		0	0
Benefits paid		(36,895)	(38,197)
Other-primarily actuarial (gain) loss		(11,267)	14,126
Benefit Obligations at end of year	313,629	228,873	270,098
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year		255,642	274,225
Actual return on plan assets		(6,463)	39,689
Employer contributions		222	429
Benefits paid		(36,895)	(38,197)
Divestitures		0	(20,504)
Value of Plan Assets at end of year	274,225	212,506	255,642
Accrued benefit cost		(16,367)	(14,456)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Accumulated gain		8,899	16,178
Total not yet recognized as a component of net periodic benefit cost		8,899	16,178
BALANCE SHEET AMOUNTS
Current liability		(220)	(420)
Noncurrent liability		(16,147)	(14,036)
Liability, Defined Benefit Plan		(16,367)	(14,456)
Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year		110,519	111,867
Service cost	180	558	671
Interest cost	978	3,674	4,150
Divestitures (see Note 5 to the Consolidated Financial Statements)		0	0
Settlement gain		0	0
Curtailments		0	(520)
Benefits paid		(5,388)	(8,152)
Other-primarily actuarial (gain) loss		(20,800)	2,503
Benefit Obligations at end of year	111,867	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		5,388	8,152
Benefits paid		(5,388)	(8,152)
Divestitures		0	0
Value of Plan Assets at end of year	$ 0	0	0
Accrued benefit cost		(88,563)	(110,519)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Accumulated gain		25,936	5,137
Total not yet recognized as a component of net periodic benefit cost		25,936	5,137
BALANCE SHEET AMOUNTS
Current liability		(5,400)	(8,150)
Noncurrent liability		(83,163)	(102,369)
Liability, Defined Benefit Plan		$ (88,563)	$ (110,519)