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Interest Rate Hedge - Notional amounts, fair values and classification (Details) - Interest rate swaps - Hedging - USD ($) $ in Millions	Sep. 30, 2018	May 09, 2018
Derivatives
Notional amount		$ 1,361.2
Cash flow hedging
Derivatives
Notional amount	$ 1,354.3
Cash flow hedging \| Other noncurrent assets
Derivatives
Derivative asset, fair value	7.2
Cash flow hedging \| Accrued liabilities and other
Derivatives
Derivative liability, fair value	$ 2.0