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Stock Options and Employee Stock Purchase Plan - Narrative (Details) - USD ($) |  |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
May 07, 2020 | May 01, 2018 | May 31, 2001 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Options exercisable (in shares) |  |  |  | 175,601 | 163,741 | 298,577
Options exercisable (in usd per share) |  |  |  | $ 60.35 | $ 45.94 | $ 32.15
Number of options granted (in shares) |  |  |  | 0 | 0 | 400,000
Weighted-average grant-date fair values of stock options granted (in usd per share) |  |  |  |  |  | $ 19.39
Total intrinsic values of options exercised in period |  |  |  | $ 3,000,000.0 | $ 10,400,000 | $ 3,800,000
Total fair value of options vested |  |  |  | 1,000,000.0 | 1,000,000.0 | 100,000
Exercise of stock options |  |  |  | 1,619,000 | 5,274,000 | 1,540,000
Tax benefit realized for the tax deductions from option exercises |  |  |  | 700,000 | 2,400,000 | 900,000
Compensation expense recognized |  |  |  | $ 24,006,000 | $ 23,922,000 | $ 28,093,000
Estimated forfeiture rates |  |  |  | 13.00% | 13.90% | 11.80%
Share-based Payment Arrangement, Option |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Terms of award |  |  |  | 10 years |  |
Award vesting periods |  |  |  | 5 years |  |
Award vesting percentage |  |  |  | 20.00% |  |
Compensation expense recognized |  |  |  | $ 900,000 | $ 900,000 | $ 900,000
Unrecognized compensation cost related to non-vested awards granted |  |  |  | $ 5,800,000 |  |
Weighted-average period to recognize compensation cost (in years) |  |  |  | 5 years |  |
Restricted Stock and Restricted Stock Unit |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Restricted stock and restricted units granted (in shares) |  |  |  | 129,786 | 117,566 | 376,799
Modification incremental compensation cost | $ 0 |  |  |  |  |
Restricted Stock and Restricted Stock Unit | Board of Directors |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Award vesting periods |  |  |  | 1 year |  |
Restricted Stock and Restricted Stock Unit | Senior Staff |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Award vesting periods |  |  |  | 5 years |  |
Restricted Stock and Restricted Stock Unit | Chief Executive Officer |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Award vesting periods |  |  |  | 8 years |  |
Market-based Restricted Stock Awards |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Weighted-average period to recognize compensation cost (in years) |  |  |  | 4 years 2 months 12 days |  |
Restricted stock and restricted units granted (in shares) |  |  |  | 82,112 | 74,051 | 473,501
Weighted-average grant-date fair values of restricted stock awards granted (in usd per share) |  |  |  | $ 70.99 | $ 69.99 | $ 52.95
Restricted Stock and Restricted Stock Unit, Market-based Restricted Stock |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Tax benefit realized for the tax deductions from option exercises |  |  |  | $ 2,100,000 | $ 2,400,000 | $ 2,400,000
Compensation expense recognized |  |  |  | 21,200,000 | 21,700,000 | 26,400,000
Unrecognized compensation cost related to non-vested awards granted |  |  |  | 38,600,000 |  |
Total fair value of restricted stock and restricted stock units vested |  |  |  | 18,600,000 | 12,700,000 | 9,700,000
Share-based compensation, dividends paid |  |  |  | $ 0 | $ 100,000 | $ 100,000
Restricted Stock Units (RSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Weighted-average period to recognize compensation cost (in years) |  |  |  | 4 years 6 months |  |
Restricted stock and restricted units granted (in shares) |  |  |  | 210,630 | 3,844 | 20,044
2015 Stock Option Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Maximum issuance of common stock (in shares) |  |  |  | 4,200,000 |  |
Number of shares available for issuance (in shares) |  |  |  | 2,019,350 |  |
2015 Stock Option Plan | Minimum |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Market value of common stock on the date of grant for incentive stock options |  |  |  | 100.00% |  |
Employee Stock Purchase Plan | Employee Stock |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Maximum issuance of common stock (in shares) |  |  | 2,000,000 |  |  |
Market value of common stock on the date of grant for incentive stock options |  | 85.00% | 95.00% |  |  |
Offering period for incentive stock options |  | 6 months | 3 months |  |  |
Number of shares available for issuance (in shares) |  |  |  | 1,404,939 |  |
Compensation expense recognized |  |  |  | $ 2,000,000.0 | $ 1,300,000 | $ 700,000
Estimated forfeiture rates |  |  |  | 11.15% | 5.80% | 1.96%
Maximum earnings withheld by the employees |  |  | 15.00% |  |  |
Issuance of shares under Employee Stock Purchase Plan (in shares) |  |  |  | 118,629 | 66,413 | 33,262
Employee Stock Purchase Plan | Minimum | Employee Stock |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Purchase price under the Purchase Plan (in usd per share) |  |  |  | $ 61.51 |  |
Employee Stock Purchase Plan | Maximum | Employee Stock |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Purchase price under the Purchase Plan (in usd per share) |  |  |  | $ 62.82 |  |

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Balance Type: |
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- Details
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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- Details
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