Employee Benefit Plans Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Components of Net Periodic Benefit Cost (Income) [Abstract]
Payment for pension benefits			$ 11,400
Pension Benefits [Member]
Components of Net Periodic Benefit Cost (Income) [Abstract]
Service cost	$ 2,779	$ 2,409	8,337	$ 7,228
Interest cost	5,710	6,622	17,130	19,866
Expected return on plan assets	(6,541)	(6,360)	(19,622)	(19,082)
Amortization of prior service cost (credit)	0	1,636	0	4,908
Recognized actuarial loss (gain)	1,257	0	3,771	0
Plan settlements	0	715	0	715
Net periodic benefit cost (credit)	3,205	5,022	9,616	13,635
Other Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost (Income) [Abstract]
Service cost	93	82	278	248
Interest cost	123	152	369	457
Expected return on plan assets	(246)	(217)	(738)	(652)
Amortization of prior service cost (credit)	(471)	(471)	(1,412)	(1,412)
Recognized actuarial loss (gain)	(15)	(24)	(45)	(72)
Plan settlements	0	0	0	0
Net periodic benefit cost (credit)	$ (516)	$ (478)	$ (1,548)	$ (1,431)