Fair Value Measurement - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Oct. 01, 2019	Oct. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charges	$ 0	$ 0
Fair Value, Measurements, Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investment balance	15,449,000		$ 15,449,000
Commercial paper | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper	56,553,000		59,243,000
Commercial paper | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper	56,553,000		59,243,000
Available-for-sale securities	4,493,000		9,586,000
5.125% Senior Notes Due 2024 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying amount of senior notes	325,000,000		325,000,000
Estimated Fair Value	312,000,000		337,188,000
Interest rate					5.125%
4.625% Senior Notes due 2027 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying amount of senior notes	300,000,000		300,000,000
Estimated Fair Value	$ 283,500,000		$ 301,500,000
Interest rate				4.625%