Pensions and Other Employee Benefits Plans (Reconciliation of Changes in Plans' Benefit Obligations and Fair Value of Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of period	$ 29,296
Fair value of plan assets at December 31,	31,466	$ 29,296
Pension Benefits [Member]
Reconciliation of benefit obligation:
Obligation at beginning of period	46,976	48,172
Service cost	668	511	$ 188
Interest cost	1,982	1,896	1,882
Participant contributions	45	22
Actuarial (gain) loss	1,537	(1,930)
Benefit payments	(1,745)	(1,695)
Obligation at December 31	49,463	46,976	48,172
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of period	29,296	28,476
Actual return on plan assets	1,709	(248)
Employer contributions	2,161	2,741
Participant contributions	45	22
Benefit payments	(1,745)	(1,695)
Fair value of plan assets at December 31,	31,466	29,296	28,476
Funded status at end of period	(17,997)	(17,680)
Other Benefits [Member]
Reconciliation of benefit obligation:
Obligation at beginning of period	559	1,623
Service cost	1	2	1
Interest cost	22	38	71
Participant contributions	20	38
Actuarial (gain) loss	(6)	(1)
Benefit payments	(52)	(92)
Curtailment and settlement		(1,049)
Obligation at December 31	544	559	$ 1,623
Reconciliation of fair value of plan assets:
Employer contributions	32	54
Participant contributions	20	38
Benefit payments	(52)	(92)
Funded status at end of period	$ (544)	$ (559)