Debt - (Details) - Senior Notes	Mar. 26, 2018 USD ($)	Dec. 18, 2017 USD ($) tranche
Note Purchase Agreement
Debt Instrument [Line Items]
Debt amount		$ 175,000,000.0
Number of issuance tranches | tranche		2
Note Purchase Agreement - 2.94%
Debt Instrument [Line Items]
Debt amount		$ 25,000,000.0
Interest rate, stated percentage (in hundredths)		2.94%
Note Purchase Agreement - 3.08%
Debt Instrument [Line Items]
Debt amount		$ 100,000,000.0
Interest rate, stated percentage (in hundredths)		3.08%
Note Purchase Agreement - 3.17%
Debt Instrument [Line Items]
Debt amount	$ 50,000,000.0
Interest rate, stated percentage (in hundredths)	3.17%