Pension and Other Postretirement Benefits - Change in Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Change in plan assets:
Fair value of plan assets, beginning of year	$ 311,509
Fair value of plan assets, end of year	355,726	$ 311,509
Pension Benefits
Change in plan assets:
Fair value of plan assets, beginning of year	311,509	198,000
Actual return on plan assets	45,896	(8,366)
Employer contributions	5,673	5,363
Plan participant contributions	86	85
Acquisitions	0	153,919
Settlements	0	(7,054)
Foreign currency exchange rate changes	9,275	(17,606)
Benefits paid	(16,713)	(12,832)
Fair value of plan assets, end of year	355,726	311,509
Other Benefits
Change in plan assets:
Fair value of plan assets, beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	1,302	1,481
Plan participant contributions	4	6
Acquisitions	0	0
Settlements	0	0
Foreign currency exchange rate changes	0	0
Benefits paid	(1,306)	(1,487)
Fair value of plan assets, end of year	$ 0	$ 0