Employee and Retiree Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Profit Sharing Plan
Defined Contribution Plan Disclosure [Line Items]
Profit sharing contributions	$ 1.5	$ (0.8)	$ 2.2
Thrift Plan
Defined Contribution Plan Disclosure [Line Items]
Company matching contribution (percent)	100.00%
Employee's maximum contribution matched by Company (percent)	6.00%
Profit sharing percentage 1	5.00%
Profit sharing percentage 2	7.00%
Profit sharing percentage 3	9.00%
Profit sharing contributions	$ 12.9	$ 9.7	$ 12.1