XML 59 R48.htm IDEA: XBRL DOCUMENT
v3.20.2

Stockholders' Equity - Share Activity by Class of Stock (Details) - shares | 6 Months Ended |
--- | --- | ---
Jun. 30, 2020 | Dec. 31, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Beginning balance (in shares) | 77,801,854 |
Shares issued (in shares) | 0 |
Restricted share award net share settlement (in shares) | (126,971) |
Delivery of Shares Underlying RSUs (in shares) | 24,233 |
Ending balance (in shares) | 78,575,100 |
Class A Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Beginning balance (in shares) | 56,429,825 |
Restricted share award net share settlement (in shares) | (126,971) |
Delivery of Shares Underlying RSUs (in shares) | 24,233 |
Ending balance (in shares) | 61,354,644 |
Class B Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Beginning balance (in shares) | 7,803,364 |
Restricted share award net share settlement (in shares) | 0 |
Delivery of Shares Underlying RSUs (in shares) | 0 |
Ending balance (in shares) | 5,589,292 |
Class C Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Beginning balance (in shares) | 13,568,665 |
Restricted share award net share settlement (in shares) | 0 |
Delivery of Shares Underlying RSUs (in shares) | 0 |
Ending balance (in shares) | 11,631,164 |
Restricted Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Shares issued (in shares) | 916,085 |
Granted (in shares) | 919,455 |
Restricted Stock | Class A Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Shares issued (in shares) | 916,085 |
Restricted Stock | Class B Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Shares issued (in shares) | 0 |
Restricted Stock | Class C Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Shares issued (in shares) | 0 |
Restricted Stock Units RSUs |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Restricted stock units outstanding (in shares) | 304,570 | 297,891
Granted (in shares) | 3,370 |
Performance Shares |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Shares issued in period (in shares) | 60,000 |
Granted (in shares) | 60,000 |
Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Holdings Common Unit Exchanges (in shares) | 0 |
Common Stock | Class A Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Holdings Common Unit Exchanges (in shares) | (2,349,247) |
Common Stock | Class B Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Holdings Common Unit Exchanges (in shares) | (403,941) |
Common Stock | Class C Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Holdings Common Unit Exchanges (in shares) | (1,945,306) |
Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Employee/Partner Terminations (in shares) | (40,101) |
Common Stock | Class A Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Employee/Partner Terminations (in shares) | (40,101) |
Common Stock | Class B Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Employee/Partner Terminations (in shares) | (32,805) |
Common Stock | Class C Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Employee/Partner Terminations (in shares) | (32,805) |
Follow On Offering |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Shares issued (in shares) | 0 |
Follow On Offering | Class A Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Shares issued (in shares) | 1,802,326 |
Follow On Offering | Class B Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Shares issued (in shares) | 1,777,326 |
Follow On Offering | Class C Common Stock |  |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |  |
Shares issued (in shares) | 25,000 |

X
- Definition Stock Issued During Period, Shares, Exchange of Securities + References No definition available. + Details
Name: | apam_StockIssuedDuringPeriodSharesExchangeofSecurities
Namespace Prefix: | apam_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_CommonStockSharesOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_IncreaseDecreaseInStockholdersEquityRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- 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=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of equity instruments other than options outstanding, including both vested and non-vested instruments. + 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)(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 2: 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)(i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of shares issued under share-based payment arrangement. + 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 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares used to settle grantee's tax withholding obligation for award under share-based payment arrangement. + References No definition available. + Details
Name: | us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares issued in lieu of cash for services contributed to the entity. Number of shares includes, but is not limited to, shares issued for services contributed by vendors and founders. + References No definition available. + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesIssuedForServices
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of new stock issued during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares that have been repurchased and retired during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 + Details
Name: | us-gaap_StockRepurchasedAndRetiredDuringPeriodShares
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassBMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | apam_HoldingsCommonUnitExchangesAxis=us-gaap_CommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | apam_EmployeePartnerTerminationsAxis=us-gaap_CommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsidiarySaleOfStockAxis=apam_FollowOnOfferingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |