Pension Benefits, Other Postretirement Benefits and Employee Savings and Investment Plans (Summary of Changes in Fair Value of Guaranteed Deposit Account's Level 3 Assets) (Details) - Pension Benefits $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at the beginning of the year	$ 191,652
Fair value of plan assets at the end of the year	42,835
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at the beginning of the year	1,360
Fair value of plan assets at the end of the year	1,338
Guaranteed deposit account
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at the beginning of the year	1,360
Fair value of plan assets at the end of the year	1,338
Guaranteed deposit account | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at the beginning of the year	1,360
Change in unrealized gain (loss)	41
Purchases, sales, issuances and settlements (net)	(63)
Fair value of plan assets at the end of the year	$ 1,338