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Stockholders' Equity - Textual (Details) $ / shares in Units, $ in Millions |  | 9 Months Ended | 12 Months Ended | 45 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Aug. 14, 2018 USD ($) $ / shares shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2020 USD ($) numberOfVote $ / shares shares | Dec. 31, 2019 USD ($) $ / shares shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2020 USD ($) numberOfVote $ / shares shares | Oct. 30, 2018 USD ($) | Apr. 25, 2018 USD ($) | Aug. 01, 2017 USD ($) | Apr. 02, 2017 shares
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |
Common Stock, shares authorized (in shares) |  |  | 450,000,000.0 | 450,000,000.0 |  | 450,000,000.0 |  |  |  |
Common Stock, par value per share (in dollars per share) | $ / shares |  |  | $ 0.01 | $ 0.01 |  | $ 0.01 |  |  |  |
Number of vote per common stock | numberOfVote |  |  | 1 |  |  | 1 |  |  |  |
Preferred Stock, shares authorized (in shares) |  |  | 100,000,000.0 |  |  | 100,000,000.0 |  |  |  |
Preferred Stock, shares outstanding (in shares) |  | 13,500,000 | 0 |  | 0 | 0 |  |  |  |
Common Stock, shares outstanding (in shares) |  | 105,200,000 | 97,800,000 | 96,900,000 | 110,400,000 | 97,800,000 |  |  |  |
Stock repurchase program, authorized amount | $ |  |  |  |  |  |  | $ 1,500.0 | $ 1,000.0 | $ 500.0 |
Treasury stock, shares, acquired (in shares) |  | 5,800,000 |  | 14,600,000 | 21,100,000 | 41,500,000 |  |  |  |
Payments for repurchase of common stock | $ |  | $ 175.7 | $ 0.0 | $ 329.9 | $ 834.7 | $ 1,340.3 |  |  |  |
Payments for commissions | $ |  | $ 0.8 |  |  |  |  |  |  |  |
Stock repurchase program, remaining authorized repurchase amount | $ |  |  | $ 160.5 |  |  | $ 160.5 |  |  |  |
Stock repurchased during period, shares |  |  | 400,000 | 15,000,000.0 | 21,500,000 |  |  |  |  |
Common Stock |  |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |
Common Stock, shares authorized (in shares) |  |  | 450,000,000.0 |  |  | 450,000,000.0 |  |  |  |
Common Stock, par value per share (in dollars per share) | $ / shares |  |  | $ 0.01 |  |  | $ 0.01 |  |  |  |
Preferred Stock |  |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |
Preferred Stock, shares authorized (in shares) |  |  | 100,000,000.0 | 100,000,000.0 |  | 100,000,000.0 |  |  |  |
Preferred Stock, par value per share (in dollars per share) | $ / shares |  |  | $ 0.01 | $ 0.01 |  | $ 0.01 |  |  |  |
Preferred Stock, shares outstanding (in shares) |  |  | 0 | 0 |  | 0 |  |  |  |
Convertible Preferred Stock |  |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |
Preferred Stock, shares authorized (in shares) |  |  |  |  |  |  |  |  |  | 50,000,000.0
Series Common Stock |  |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |
Common Stock, shares authorized (in shares) |  |  | 50,000,000.0 | 50,000,000.0 |  | 50,000,000.0 |  |  |  |
Common Stock, par value per share (in dollars per share) | $ / shares |  |  | $ 0.01 | $ 0.01 |  | $ 0.01 |  |  |  |
Common Stock, shares outstanding (in shares) |  |  | 0 | 0 |  | 0 |  |  |  |
Treasury Stock |  |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |
Payments for repurchase of common stock | $ | $ 300.0 |  |  |  |  |  |  |  |  |
Stock repurchased during period, shares | 7,200,000 |  |  |  |  |  |  |  |  |
Treasury stock acquired, average cost (in dollars per share) | $ / shares | $ 41.82 |  |  |  |  |  |  |  |  |
Share repurchase discount percentage | 1.70% |  |  |  |  |  |  |  |  |
Shares relinquished, shares |  |  | 400,000 | 400,000 | 400,000 |  |  |  |  |

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