Debt - Credit Agreement (Details) - USD ($)				6 Months Ended
	Jun. 18, 2020	Apr. 24, 2020	Feb. 12, 2016	Jun. 28, 2020	Apr. 23, 2020	Jun. 18, 2010
Letters of credit
Credit Agreement
Term of debt				1 year
Stand-by letters of credit outstanding				$ 16,300,000
Credit Agreement
Credit Agreement
Borrowing capacity		$ 100,000,000
Term of debt			5 years
Sublimit on letters of credit			$ 100,000,000
Eurocurrency rate loans | LIBOR
Credit Agreement
Minimum base rate (as a percent)		$ 1.00
Eurocurrency rate loans | LIBOR | Minimum
Credit Agreement
Interest rate added to base rate (as a percent)		1.50%
Eurocurrency rate loans | LIBOR | Maximum
Credit Agreement
Interest rate added to base rate (as a percent)		2.10%
Base rate loans and swing line loans
Credit Agreement
Minimum base rate (as a percent)		$ 2.00
Base rate loans and swing line loans | LIBOR
Credit Agreement
Interest rate (as a percent)		1.00%
Base rate loans and swing line loans | Prime Rate
Credit Agreement
Interest rate (as a percent)		0.50%
Revolving credit facility
Credit Agreement
Borrowing capacity		$ 800,000,000	$ 500,000,000		$ 500,000,000
Extension period		1 year
Interest rate on revolving credit facility (as a percent)				2.50%
Amount drawn				$ 265,000,000.0
Unused and available credit under the credit agreement				518,700,000
Borrowings outstanding				16,300,000
Term loan facility | Term Loan due February 2021
Credit Agreement
Term of debt			5 years
Face amount			$ 300,000,000
Amount drawn				$ 300,000,000
Notes Purchase Agreement 2010 | Revolving credit facility
Credit Agreement
Repayment of debt	$ 35,000,000.0
Notes Purchase Agreement 2010 | Senior notes
Credit Agreement
Face amount						$ 75,000,000.0
Amount drawn	$ 40,000,000.0
Swing Line Loans
Credit Agreement
Borrowing capacity		$ 15,000,000