Fiduciary Assets and Liabilities	9 Months Ended
Sep. 30, 2018
Fiduciary Assets And Liabilities [Abstract]
Fiduciary Assets and Liabilities	Fiduciary Assets and Liabilities In its capacity as an insurance broker or agent, the Company collects premiums from insureds and, after deducting its commissions, remits the premiums to the respective insurance underwriters. The Company also collects claims or refunds from underwriters on behalf of insureds. Unremitted insurance premiums and claims proceeds are held by the Company in a fiduciary capacity. Risk and Insurance Services revenue includes interest on fiduciary funds of $18 million and $46 million for the three and nine months ended September 30, 2018, respectively, and $11 million and $28 million for the three and nine month periods ended September 30, 2017, respectively. The Consulting segment recorded fiduciary interest income of $1 million and $3 million for the three and nine months ended September 30, 2018, respectively, and $2 million and $3 million for the three and nine months ended September 30, 2017, respectively. Since fiduciary assets are not available for corporate use, they are shown in the consolidated balance sheets as an offset to fiduciary liabilities. Net uncollected premiums and claims and the related payables amounted to $7.8 billion at September 30, 2018 and $6.8 billion at December 31, 2017. The Company is not a principal to the contracts under which the right to receive premiums or the right to receive reimbursement of insured losses arises. Accordingly, net uncollected premiums and claims and the related payables are not assets and liabilities of the Company and are not included in the accompanying consolidated balance sheets. In certain instances, the Company advances premiums, refunds or claims to insurance underwriters or insureds prior to collection. These advances are made from corporate funds and are reflected in the accompanying consolidated balance sheets as receivables.

Fiduciary Assets and Liabilities

In its capacity as an insurance broker or agent, the Company collects premiums from insureds and, after deducting its commissions, remits the premiums to the respective insurance underwriters. The Company also collects claims or refunds from underwriters on behalf of insureds. Unremitted insurance premiums and claims proceeds are held by the Company in a fiduciary capacity. Risk and Insurance Services revenue includes interest on fiduciary funds of $18 million and $46 million for the three and nine months ended September 30, 2018, respectively, and $11 million and $28 million for the three and nine month periods ended September 30, 2017, respectively. The Consulting segment recorded fiduciary interest income of $1 million and $3 million for the three and nine months ended September 30, 2018, respectively, and $2 million and $3 million for the three and nine months ended September 30, 2017, respectively. Since fiduciary assets are not available for corporate use, they are shown in the consolidated balance sheets as an offset to fiduciary liabilities.

Net uncollected premiums and claims and the related payables amounted to $7.8 billion at September 30, 2018 and $6.8 billion at December 31, 2017. The Company is not a principal to the contracts under which the right to receive premiums or the right to receive reimbursement of insured losses arises. Accordingly, net uncollected premiums and claims and the related payables are not assets and liabilities of the Company and are not included in the accompanying consolidated balance sheets.

In certain instances, the Company advances premiums, refunds or claims to insurance underwriters or insureds prior to collection. These advances are made from corporate funds and are reflected in the accompanying consolidated balance sheets as receivables.