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Stock-Based Compensation - Restricted Stock Units (Details) - Restricted stock units - USD ($) $ / shares in Units, $ in Millions | 6 Months Ended
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Jun. 30, 2020 | Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Vested in period, fair value | $ 21.5 | $ 6.3
Number of Shares (in shares) |  |
Unvested at beginning of period (in shares) | 3,039,020 |
Granted (in shares) | 882,672 |
Forfeited (in shares) | (243,540) |
Vested (in shares) | (671,435) |
Unvested at end of period (in shares) | 3,006,717 |
Weighted- Average Grant Date Fair Value (in dollars per share) |  |
Unvested at beginning of period (in dollars per share) | $ 31.39 |
Granted (in dollars per share) | 43.00 |
Forfeited (in dollars per share) | 37.02 |
Vested (in dollars per share) | 31.90 |
Unvested at end of period (in dollars per share) | $ 35.09 |
Number of vested shares recipient elected to defer settlement (in shares) | 409,302 |
Number of vested shares recipients elected to defer settlement, released during period (in shares) | 7,420 |
Number of deferred shares vested and outstanding (in shares) | 939,084 |
Unrecognized compensation expense | $ 69.9 |
Unrecognized compensation expense, period for recognition (years) | 2 years 7 months 6 days |
Minimum |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Award vesting period (years) | 3 years |
Maximum |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Award vesting period (years) | 4 years |
Cliff-vesting |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Award vesting period (years) | 3 years |
Cliff-vesting | Board of Directors |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Award vesting period (years) | 1 year |

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- Definition Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + 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 (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Amount of cost to be recognized for 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 (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + 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 (a)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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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=120381028&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=120381028&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=120381028&loc=d3e5070-113901 + Details
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