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Share-based Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Compensation cost | $ 13.8 | $ 18.9 | $ 20.9
Income tax benefit from compensation cost | $ 1.7 | $ 2.7 | $ 3.0
Shares [Roll Forward] |  |  |
Restricted stock outstanding at end of period (in shares) | 4,100,000 |  |
Restricted Stock/Restricted Stock Units |  |  |
Weighted average grant date fair market value [Abstract] |  |  |
Restricted stock outstanding at end of period (in dollars per share) | $ 12.81 |  |
Granted (in dollars per share) | 13.62 | $ 11.92 | $ 15.69
Vested (in dollars per share) | 11.67 |  |
Forfeited (in dollars per share) | 13.24 |  |
Restricted stock outstanding at end of period (in dollars per share) | $ 13.57 | $ 12.81 |
Shares [Roll Forward] |  |  |
Restricted stock outstanding at beginning of period (in shares) | 4,150,394 |  |
Granted (in shares) | 1,672,060 |  |
Vested (in shares) | (1,564,843) |  |
Forfeited (in shares) | (118,368) |  |
Restricted stock outstanding at end of period (in shares) | 4,139,243 | 4,150,394 |
Additional disclosures [Abstract] |  |  |
Total fair value of restricted stock vested | $ 20.4 | $ 13.7 | $ 19.1
Unrecognized compensation cost | $ 25.8 |  |
RSUs subject to performance conditions |  |  |
Shares [Roll Forward] |  |  |
Restricted stock outstanding at end of period (in shares) | 3,100,000 |  |
Additional disclosures [Abstract] |  |  |
Unrecognized compensation cost | $ 19.8 |  |
RSUs subject only to service conditions |  |  |
Shares [Roll Forward] |  |  |
Restricted stock outstanding at end of period (in shares) | 1,000,000.0 |  |
Additional disclosures [Abstract] |  |  |
Unrecognized compensation cost | $ 5.9 |  |
Weighted-average period for recognition of compensation cost | 1 year 8 months 12 days |  |
2020 Plan |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Maximum number of shares can be awarded under the plan (in shares) | 11,000,000.0 |  |
Shares available for future grants (in shares) | 11,100,000 |  |
Minimum |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Award vesting period | 1 year |  |
Maximum |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Award vesting period | 3 years |  |

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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(3) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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