Debt (Bilateral Credit Facilities) (Details) - Line of Credit - Bilateral credit facilities $ in Millions	Dec. 31, 2019 USD ($)	Dec. 31, 2019 EUR (€)	Sep. 30, 2019 EUR (€)	Dec. 31, 2018 USD ($)
Line of Credit Facility [Line Items]
Long-term Debt, Gross | $	$ 0.0			$ 0.0
Bilateral credit facility expiring in May 2019, tranche one
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		€ 80,000,000.0
Bilateral credit facility expiring in June 2019
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			€ 60,000,000.0
Bilateral credit facility expiring in May 2021
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			€ 100,000,000.0
Bilateral Credit Facility Expiring in May 2019 (2) [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		€ 80,000,000