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Debt and Finance Leases - Issuance of Convertible Senior Notes (Details) | 3 Months Ended
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Jun. 30, 2018 USD ($) $ / shares
Debt Instrument [Line Items] |
Debt issuance transaction costs | $ 12,000,000
Convertible Senior Notes Due 2048 | Convertible Debt |
Debt Instrument [Line Items] |
Aggregate principal amount | $ 575,000,000
Interest rate, stated percentage | 2.75%
Conversion price per common share (in usd per share) | $ / shares | $ 47.74
Conversion ratio | 20.9479
Debt, estimated fair value | $ 472,000,000
Carrying amount of equity component | $ 103,000,000
Debt discount amortization period | 7 years
Debt deferred financing costs amortization period | 7 years
Convertible Senior Notes Due 2048 | Convertible Debt | Additional Paid-in Capita |
Debt Instrument [Line Items] |
Debt issuance transaction costs | $ 2,000,000
Convertible Senior Notes Due 2048 | Convertible Debt | Deferred Financing Costs |
Debt Instrument [Line Items] |
Debt issuance transaction costs | $ 10,000,000

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