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Senior Notes - Principal Terms of Senior Notes Outstanding (Details) - Senior Notes $ in Millions | Dec. 31, 2017 USD ($) | [1]
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2024 Senior Notes |
Debt Instrument |
Par value (in millions) | $ 400.0
Stated coupon | 4.25%
2025 Senior Notes |
Debt Instrument |
Par value (in millions) | $ 350.0
Stated coupon | 3.50%
[1] | The senior notes may be redeemed at any time, in whole or in part, at a make-whole redemption price plus accrued and unpaid interest.

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