Debt (Details)						3 Months Ended
	Apr. 22, 2020 USD ($)	Apr. 06, 2020 USD ($)	Apr. 01, 2020 USD ($) numberOfBanks	Mar. 19, 2020	Mar. 18, 2020 USD ($)	Mar. 29, 2020 USD ($)	May 06, 2020 USD ($)	Dec. 31, 2019 USD ($)	[1]
Line of Credit Facility [Line Items]
Cash and cash equivalents						$ 123,335,000		$ 145,283,000
Subsequent Event
Line of Credit Facility [Line Items]
Debt maturities expected in 2021							$ 871,000,000
Cash and cash equivalents							750,000,000
Committed availability under credit facilities							$ 500,000,000
Revolving Credit Facility | Wells Fargo Bank, NA | Subsequent Event
Line of Credit Facility [Line Items]
Proceeds from lines of credit			$ 250,000,000
Maximum borrowing capacity			$ 500,000,000
Number of banks in syndicate | numberOfBanks			8
Loans payable with Wells Fargo Bank, NA | Term loan | Wells Fargo Bank, NA
Line of Credit Facility [Line Items]
Debt term					364 days
Debt principal					$ 150,000,000	$ 200,000,000
Term extension				364 days
Loans payable with Wells Fargo Bank, NA | Term loan | Wells Fargo Bank, NA | LIBOR
Line of Credit Facility [Line Items]
Basis points (percent)						1.25%
Loans payable with Wells Fargo Bank, NA | Term loan | U.S. Bank, NA | Subsequent Event | LIBOR
Line of Credit Facility [Line Items]
Basis points (percent)		1.25%
Loans Payable with U.S. Bank, NA | Term loan | U.S. Bank, NA | Subsequent Event
Line of Credit Facility [Line Items]
Debt term		364 days
Debt principal		$ 100,000,000
Repayments of commercial paper			$ 85,000,000
3.125% Notes | Notes | Subsequent Event
Line of Credit Facility [Line Items]
Debt principal	$ 600,000,000
Interest rate (percent)	3.125%
Proceeds from debentures issued	$ 594,200,000

[1] The year-end condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America.