Employee Benefits - Benefit Obligation and Plan Assets Deriving Funded Status (Details) - USD ($) $ in Thousands			12 Months Ended
	Sep. 07, 2018	Dec. 19, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in Projected Benefit Obligation
Projected benefit obligation at beginning of year			$ 95,200	$ 106,664
Interest cost			3,987	3,882	$ 4,100
Actuarial gain/(loss)			13,996	(7,371)
Acquisitions - DNB merger			6,778	0
Benefits paid			(6,282)	(7,975)
Projected Benefit Obligation at End of Year			113,679	95,200	106,664
Change in Plan Assets
Fair value of plan assets at beginning of year			101,765	87,154
Actual return on plan assets			16,358	2,166
Employer contributions	$ 20,400		0	20,420
Acquisitions - DNB merger			4,811	0
Benefits paid		$ (1,500)	(6,282)	(7,975)
Fair Value of Plan Assets at End of Year			116,652	101,765	$ 87,154
Funded Status			$ 2,973	$ 6,565