Commitments And Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2019	Dec. 30, 2014
Loss Contingencies [Line Items]
Commitment for property and equipment purchases			$ 176.5
Loss contingency, damages awarded, value		$ 0.8
Loss contingency, damages awarded, attorney fees and costs		$ 0.5
May 17, 2018 Verdict [Member]
Loss Contingencies [Line Items]
Loss contingency, damages awarded, value	$ 92.0
Self insurance retained liability				$ 10.0
Loss contingency, estimate of possible loss	15.2		17.1
Loss contingency, receivable, noncurrent	79.2		79.2
Loss contingency, accrual, noncurrent	$ 79.2		$ 79.2