Subsequent Events (Notes)	9 Months Ended
Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Business Partnerships On October 1, 2021, the Company purchased certain assets and intellectual and intangible rights and assumed certain liabilities of White Hill Plaza, Inc. (operating as K&S Insurance Agency, “K&S”) for upfront consideration consisting of $79.9 million of cash (which was reduced by the value of shares of Class A common stock issued to K&S colleagues in connection with the Partnership) and 1,018,874 LLC Units (and the corresponding 1,018,874 shares of Class B common stock). K&S will also have the opportunity to receive additional contingent consideration payable in cash, shares of Class A common stock, or a combination of both at the Company’s sole option. The Partnership brings to the Company deep expertise in the construction industry, and incremental scale in Texas. The Company has not yet completed its evaluation and determination of consideration paid, certain assets and liabilities acquired, or treatment of this transaction as either a business combination or asset acquisition in accordance with Topic 805. On October 1, 2021, the Company purchased certain assets and intellectual and intangible rights and assumed certain liabilities of Jacobson, Goldfarb & Scott, Inc., including the equity interests of certain of its subsidiaries (collectively, operating as “JGS”) for upfront consideration consisting of $157.2 million of cash (which was reduced by the value of shares of Class A common stock issued to JGS colleagues in connection with the Partnership) and 1,821,625 LLC Units (and the corresponding 1,821,625 shares of Class B common stock). JGS will also have the opportunity to receive additional contingent consideration payable in cash, shares of Class A common stock, or a combination of both at the Company’s sole option. The Partnership expands the Company’s Specialty and Middle Market practice expertise in key markets and industries, including Habitational Real Estate, Construction and Manufacturing & Distribution. The Company has not yet completed its evaluation and determination of consideration paid, certain assets and liabilities acquired, or treatment of this transaction as either a business combination or asset acquisition in accordance with Topic 805.

On October 1, 2021, the Company purchased certain assets and intellectual and intangible rights and assumed certain liabilities of White Hill Plaza, Inc. (operating as K&S Insurance Agency, “K&S”) for upfront consideration consisting of $79.9 million of cash (which was reduced by the value of shares of Class A common stock issued to K&S colleagues in connection with the Partnership) and 1,018,874 LLC Units (and the corresponding 1,018,874 shares of Class B common stock). K&S will also have the opportunity to receive additional contingent consideration payable in cash, shares of Class A common stock, or a combination of both at the Company’s sole option. The Partnership brings to the Company deep expertise in the construction industry, and incremental scale in Texas. The Company has not yet completed its evaluation and determination of consideration paid, certain assets and liabilities acquired, or treatment of this transaction as either a business combination or asset acquisition in accordance with Topic 805.

On October 1, 2021, the Company purchased certain assets and intellectual and intangible rights and assumed certain liabilities of Jacobson, Goldfarb & Scott, Inc., including the equity interests of certain of its subsidiaries (collectively, operating as “JGS”) for upfront consideration consisting of $157.2 million of cash (which was reduced by the value of shares of Class A common stock issued to JGS colleagues in connection with the Partnership) and 1,821,625 LLC Units (and the corresponding 1,821,625 shares of Class B common stock). JGS will also have the opportunity to receive additional contingent consideration payable in cash, shares of Class A common stock, or a combination of both at the Company’s sole option. The Partnership expands the Company’s Specialty and Middle Market practice expertise in key markets and industries, including Habitational Real Estate, Construction and Manufacturing & Distribution. The Company has not yet completed its evaluation and determination of consideration paid, certain assets and liabilities acquired, or treatment of this transaction as either a business combination or asset acquisition in accordance with Topic 805.