Pension Benefits, Other Postretirement Benefits and Employee Savings and Investment Plans (Obligations and Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in plan benefit obligations:
Pension settlements	$ (103)	$ (25,354)	$ (906)
Change in plan assets:
Employer contributions		25,000
Pension settlements	(103)	(25,354)	(906)
Pension Benefits
Change in plan benefit obligations:
Benefit obligation as of January 1	172,608	185,760
Service cost	0	0	0
Interest cost	5,641	6,758	7,356
Actuarial (gain) loss	23,797	(10,805)
Benefit payments	(9,262)	(9,105)
Pension settlements	(162,484)	0
Benefit obligation as of December 31	30,300	172,608	185,760
Change in plan assets:
Fair value of plan assets at the beginning of the year	191,652	180,056
Actual return on plan assets	22,888	(4,299)
Employer contributions	41	25,000
Benefit payments	(9,262)	(9,105)
Pension settlements	(162,484)	0
Fair value of plan assets at the end of the year	42,835	191,652	180,056
Amount overfunded (underfunded)	12,535	19,044
Other Postretirement Benefits
Change in plan benefit obligations:
Benefit obligation as of January 1	1,803	2,037
Service cost	61	73	80
Interest cost	59	62	71
Actuarial (gain) loss	(51)	(5)
Benefit payments	(273)	(364)
Pension settlements	0	0
Benefit obligation as of December 31	1,599	1,803	2,037
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	273	364
Benefit payments	(273)	(364)
Pension settlements	0	0
Fair value of plan assets at the end of the year	0	0	$ 0
Amount overfunded (underfunded)	$ (1,599)	$ (1,803)