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Fair Value Measurements - Changes in Level 3 Financial Assets and Liabilities (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Contingent Payment Arrangements |  |  |
Changes in level 3 assets and liabilities |  |  |
Balance, beginning of period |  | $ 1.9 | $ 9.4
Net realized and unrealized (gains) losses | [1] | 0.1 | 1.3
Purchases and issuances | [2] | 0.0 | 0.0
Settlements and reductions |  | (2.0) | (8.8)
Balance, end of period |  | 0.0 | 1.9
Net change in unrealized (gains) losses relating to instruments still held at the reporting date |  | 0.0 | 0.2
Affiliate Equity Repurchase Obligations |  |  |
Changes in level 3 assets and liabilities |  |  |
Balance, beginning of period |  | 36.2 | 49.2
Net realized and unrealized (gains) losses | [1] | 0.1 | 0.0
Purchases and issuances | [2] | 118.6 | 105.4
Settlements and reductions |  | (135.1) | (118.4)
Balance, end of period |  | 19.8 | 36.2
Net change in unrealized (gains) losses relating to instruments still held at the reporting date |  | $ 0.0 | $ 0.0
[1] | Accretion expense for these arrangements is recorded in Interest expense.
[2] | Includes transfers from Redeemable non-controlling interests.

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