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Income Taxes - Changes in Valuation Allowance (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Movement in Valuation Allowances and Reserves [Roll Forward] |  |  |
Balance, valuation allowance | $ 499.4 | $ 492.4 | $ 552.5
Remeasurement of deferred tax assets | 0.0 | 0.0 | (41.6)
Release of valuation allowance | 0.0 | 0.0 | 0.0
Expiration of net operating losses | (13.2) | (11.7) | (10.8)
Other change in valuation allowance | (0.4) | 18.7 | (7.7)
Balance, valuation allowance | $ 485.8 | $ 499.4 | $ 492.4

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