Pension, Other Postretirement Benefits and Employee Savings and Investment Plans (Obligations and Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Change in benefit obligation:
Benefit obligation at beginning of year	$ 185,760	$ 177,696
Service cost	0	0	$ 0
Interest cost	6,758	7,356	7,530
Actuarial (gain) loss	(10,805)	9,601
Benefit payments	(9,105)	(8,893)
Plan amendment	0	0
Benefit obligation at end of year	172,608	185,760	177,696
Change in plan assets:
Fair value of plan assets at the beginning of the year	180,056	171,778
Actual return on plan assets	(4,299)	16,799
Employer contributions	25,000	372
Benefit payments	(9,105)	(8,893)
Fair value of plan assets at the end of the year	191,652	180,056	171,778
Funding status	19,044	(5,704)
Retirement Health and Life Insurance Benefits
Change in benefit obligation:
Benefit obligation at beginning of year	2,037	2,504
Service cost	73	80	133
Interest cost	62	71	75
Actuarial (gain) loss	(5)	460
Benefit payments	(364)	(533)
Plan amendment	0	(545)
Benefit obligation at end of year	1,803	2,037	2,504
Change in plan assets:
Fair value of plan assets at the beginning of the year	0	0
Actual return on plan assets	0	0
Employer contributions	364	533
Benefit payments	(364)	(533)
Fair value of plan assets at the end of the year	0	0	$ 0
Funding status	$ (1,803)	$ (2,037)