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Stock-Based Compensation - Schedule of Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock compensation expense | $ 8.9 | $ 7.5 | $ 8.0 |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] |  |  |  |
Vested, number of shares | (52,466) |  |  |
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 | $ 1,986.6 | 1,959.8 | 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 | 241,306 |  |  | 14,355
Stock compensation expense | $ 8.9 | $ 7.5 | 8.0 |
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 | 524,829 |  |  |
Granted, number of shares | 241,306 |  |  |
Vested, number of shares | (172,079) |  |  |
Forfeited, number of shares | (73,044) |  |  |
Canceled, number of shares | 0 |  |  |
Restricted stock, end of year, number of shares | 521,012 | 524,829 |  |
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) | $ 33.65 |  |  |
Granted, weighted average grant date fair value (in dollars per share) |  | $ 48.47 |  |
Vested, weighted average grant date fair value (in dollars per share) |  | 38.88 |  |
Forfeited, weighted average grant date fair value (in dollars per share) |  | 38.40 |  |
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) | $ 39.73 | $ 33.65 |  |
Tax benefits from stock-based compensation | $ (0.3) | $ (0.1) | (0.4) |
Unrecognized compensation cost related to nonvested restricted stock awards | $ 10.5 |  |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition | 1 year 2 months 12 days |  |  |
Common Stock |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock compensation expense | $ 8.9 | 7.5 | 8.0 |
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 | $ 945.0 | $ 941.1 | $ 1,049.3 | $ 866.7
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 | 65,660 |  |  |
Upon One-Third Annual Anniversary | Restricted Stock |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock issued during period, shares, restricted stock award | 95,631 |  |  |
Upon Achievement of Performance Goals | Restricted Stock |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock issued during period, shares, restricted stock award | 131,320 |  |  |
Upon Achievement of Defined Return on Equity Performance Goals | Restricted Stock |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock issued during period, shares, restricted stock award | 65,660 |  |  |

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- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=122041274&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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