Employee and Retiree Benefit Plans - Projected Benefit Obligations, Accumulated Benefit Obligations and Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Funded Plan | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligations	$ 688,249	$ 457,446
Accumulated Benefit Obligations	676,177	447,793
Fair Value of Plan Assets	525,108	316,543
Unfunded Plan | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligations	108,401	94,808
Accumulated Benefit Obligations	108,401	94,808
Fair Value of Plan Assets	0	0
Unfunded Plan | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligations	177,999	158,228
Accumulated Benefit Obligations	171,934	150,586
Fair Value of Plan Assets	$ 0	$ 0