Debt (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
		Mar. 12, 2020	Mar. 31, 2020	Dec. 31, 2019	Jul. 19, 2019	Mar. 31, 2019
Debt instruments [Line Items]
Amounts drawn on revolving credit facility			$ 1,140,000	$ 883,500
Revolving credit facility, increase		$ 238,000
Cash and cash equivalents			310,146	$ 73,620		$ 61,529
Revolving credit facility, current commitment			1,150,000
Revolving credit facility, maximum commitment			$ 1,425,000
Weighted-average interest rate at period end			3.01%	3.03%
Daily average amount outstanding			$ 923,423	$ 925,715
Weighted-average interest rate			2.83%	3.54%
Outstanding letters of credit	[1]		$ (5,428)
Net available for borrowing as of March 31, 2020			$ 4,572
Revolving credit facility [Member]
Debt instruments [Line Items]
Maximum leverage ratio			3.5
Minimum ratio of EBIT to interest expense			3.0
Ratio of total debt less unrestricted cash to EBITDA			2.75
Interest rate swap [Member]
Debt instruments [Line Items]
Interest rate swap amount					$ 200,000
Minimum [Member]
Debt instruments [Line Items]
Revolving credit facility, commitment fee			0.175%
Maximum [Member]
Debt instruments [Line Items]
Revolving credit facility, commitment fee			0.35%

[1] We use standby letters of credit to collateralize certain obligations related primarily to our self-insured workers’ compensation claims, as well as claims for environmental matters, as required by certain states. These letters of credit reduce the amount available for borrowing under our revolving credit facility.