Pension Benefits, Other Postretirement Benefits and Employee Savings and Investment Plans (Obligations and Funded Status) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Change in plan benefit obligations:
Benefit obligation as of January 1	$ 30,300,000	$ 172,608,000
Service cost		0	$ 0
Interest cost	908,000	5,641,000	6,758,000
Actuarial (gain) loss	491,000	23,797,000
Benefit payments	(1,647,000)	(9,262,000)
Pension settlements	237,000	(162,484,000)
Benefit obligation as of December 31	30,289,000	30,300,000	172,608,000
Change in plan assets:
Fair value of plan assets as of January 1	42,835,000	191,652,000
Actual return on plan assets	3,615,000	22,888,000
Employer contributions	0	41,000
Benefit payments	(1,647,000)	(9,262,000)
Transfer related to plan termination	(9,744,000)	0
Pension settlements	237,000	(162,484,000)
Fair value of plan assets as of December 31	35,296,000	42,835,000	191,652,000
Amount overfunded (underfunded)	5,007,000	12,535,000
Other Postretirement Benefits
Change in plan benefit obligations:
Benefit obligation as of January 1	1,599,000	1,803,000
Service cost	56,000	61,000	73,000
Interest cost	40,000	59,000	62,000
Actuarial (gain) loss	0	(51,000)
Benefit payments	(192,000)	(273,000)
Pension settlements	0	0
Benefit obligation as of December 31	1,503,000	1,599,000	1,803,000
Change in plan assets:
Fair value of plan assets as of January 1	0	0
Actual return on plan assets	0	0
Employer contributions	192,000	273,000
Benefit payments	(192,000)	(273,000)
Transfer related to plan termination	0	0
Pension settlements	0	0
Fair value of plan assets as of December 31	0	0	$ 0
Amount overfunded (underfunded)	$ (1,503,000)	$ (1,599,000)