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Stock-Based Compensation - Schedule of Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Stock compensation expense | $ 8.0 | $ 5.6 | $ 3.8
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |
Ending Balance | $ 2,013.9 | 1,693.9 |
Restricted Stock |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Stock issued during period, shares, restricted stock award | 230,922 |  |
Stock compensation expense |  | $ 5.6 | 3.3
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] |  |  |
Restricted stock, beginning of year, number of shares | 380,584 |  |
Granted, number of shares | 230,922 |  |
Vested, number of shares | (202,286) |  |
Forfeited, number of shares | (46,198) |  |
Canceled, number of shares | 0 |  |
Restricted stock, end of year, number of shares | 363,022 | 380,584 |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |
Restricted stock, beginning of year, weighted-average measurement date fair value (in dollars per share) | $ 37.46 |  |
Granted, weighted average grant date fair value (in dollars per share) |  | $ 41.29 |
Vested, weighted average grant date fair value (in dollars per share) |  | 33.24 |
Forfeited, weighted average grant date fair value (in dollars per share) |  | 41.18 |
Canceled, weighted average grant date fair value (in dollars per share) |  | 0 |
Restricted stock, end of year, weighted-average measurement date fair value (in dollars per share) | $ 41.47 | $ 37.46 |
Tax benefits from stock-based compensation | $ 0.4 | $ 0.2 | 0.6
Unrecognized compensation cost related to nonvested restricted stock awards | $ 8.1 |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition | 1 year 1 month 6 days |  |
Common Stock |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Stock compensation expense | $ 8.0 | $ 5.6 | $ 3.8
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |
Ending Balance | $ 1,049.3 |  |
Upon Achievement of Defined Total Return to Shareholder Goals | Restricted Stock |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Stock issued during period, shares, restricted stock award | 36,463 |  |

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