Pension and Post-Retirement Benefits - Changes in Benefit Obligations and Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at January 1,	$ 102,396
Fair value of plan assets at December 31,	110,431	$ 102,396
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1,	138,900	122,052
Service cost	1,304	1,307	$ 1,037
Interest cost	5,375	4,632	3,971
Actuarial (gain) loss	17,225	(10,263)
Benefits paid	(14,922)	(8,202)
Other	609	29,374
Benefit obligation at December 31,	148,491	138,900	122,052
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at January 1,	102,396	92,067
Actual return on plan assets	17,919	(6,204)
Employer contributions	4,755	3,350
Benefits paid	(14,922)	(8,202)
Other	283	21,385
Fair value of plan assets at December 31,	110,431	102,396	92,067
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	(38,060)	(36,504)
Post-retirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1,	21,570	22,771
Service cost	88	102	107
Interest cost	789	740	753
Actuarial (gain) loss	206	(965)
Benefits paid	(815)	(1,499)
Other	216	421
Benefit obligation at December 31,	22,054	21,570	22,771
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at January 1,	0	0
Actual return on plan assets	0	0
Employer contributions	599	1,078
Benefits paid	(815)	(1,499)
Other	216	421
Fair value of plan assets at December 31,	0	0	$ 0
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	$ (22,054)	$ (21,570)