Pensions and Other Employee Benefits Plans (Fair Values of Pension Plan Assets) (Details) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets		$ 41,457	$ 38,146
Pension plans' actual assets allocation		100.00%	100.00%
Liquid Return Seeking [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans' actual assets allocation		61.00%
Multi Asset Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[1]	$ 25,196	$ 23,127
Pension plans' actual assets allocation	[1]	61.00%	61.00%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans' actual assets allocation		29.00%
Commingled Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[2]	$ 11,881	$ 11,463
Pension plans' actual assets allocation	[2]	29.00%	30.00%
Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets		$ 4,380	$ 3,556
Pension plans' actual assets allocation		10.00%	9.00%
Equity Long/Short Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[3]	$ 2,201	$ 1,349
Pension plans' actual assets allocation	[3]	5.00%	4.00%
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[4]	$ 22	$ 48
Pension plans' actual assets allocation	[4]	0.00%	0.00%
Distressed Opportunity Ltd. Partnership [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[5]	$ 433	$ 463
Pension plans' actual assets allocation	[5]	1.00%	1.00%
Multi-Strategy Limited Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[6]	$ 1,724	$ 1,696
Pension plans' actual assets allocation	[6]	4.00%	4.00%
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets		$ 4,380	$ 3,556	$ 3,143
Level 3 [Member] | Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets		4,380	3,556
Level 3 [Member] | Equity Long/Short Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[3]	2,201	1,349
Level 3 [Member] | Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[4]	22	48
Level 3 [Member] | Distressed Opportunity Ltd. Partnership [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[5]	433	463
Level 3 [Member] | Multi-Strategy Limited Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[6]	1,724	1,696
Assets Measured at Net Asset Value (NAV) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[7]	37,077	34,590
Assets Measured at Net Asset Value (NAV) [Member] | Multi Asset Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[1],[7]	25,196	23,127
Assets Measured at Net Asset Value (NAV) [Member] | Commingled Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[2],[7]	$ 11,881	$ 11,463

[1] A single fund that invests in global equities, marketable real assets and fixed income securities. The fund has no limitation on redemptions.

[2] Investments in bonds representing many sectors of the broad bond market with both short-term and intermediate-term maturities. The fund has no limitation on redemptions.

[3] Investments primarily in long and short positions in equity securities of U.S. and non-U.S. companies. The fund generally has semi-annual tender offer redemption periods on June 30 and December 31 and is reported on a one month lag.

[4] Fund invests in portfolios of secondary interest in established venture capital, buyout, mezzanine and special situation funds on a global basis. Fund is valued on a quarterly lag with adjustment for subsequent cash activity. The fund terminates on July 12, 2021, subject to extension for a one-year period. Earlier redemptions are not permitted.

[5] Investments mainly in discounted debt securities, bank loans, trade claims and other debt and equity securities of financially troubled companies. This partnership has semi-annual withdrawal rights on June 30 and December 31 with notice of 90 days and is reported on a one month lag.

[6] Investments in a partnership that has a multi-strategy investment program and does not rely on a single investment model. This partnership has quarterly redemption rights with notice of 65 days and is reported on a one month lag.

[7] Assets measured using the net asset value (“NAV”) practical expedient have not been classified in the fair value hierarchy. The NAV practical expedient is based on the fair value of the underlying assets of the common/collective trust (“CCT”) minus its liabilities, and then divided by the number of units outstanding. The NAV practical expedient of a CCT is calculated based on a compilation of primarily observable market information.