Debt	3 Months Ended
Mar. 31, 2015
Debt Disclosure [Abstract]
Debt	Debt Revolving Credit Facilities As of December 31, 2014, Aon plc had two primary committed credit facilities outstanding: its $400 million U.S. credit facility expiring in March 2017 (the "2017 Facility") and its €650 million ($707 million based on exchange rates at March 31, 2015) European credit facility expiring in October 2015 (the "2015 Facility"). Aon Corporation entered into the 2015 Facility on October 15, 2010 (Aon plc became a borrower under such facility on April 29, 2013) and Aon plc entered into the 2017 Facility on March 20, 2012. On February 2, 2015, Aon plc replaced the 2015 Facility with a new $900 million multi-currency U.S. credit facility expiring in February 2020 (the "2020 Facility"). Each of these facilities included customary representations, warranties and covenants, including financial covenants that require Aon plc to maintain specified ratios of adjusted consolidated EBITDA to consolidated interest expense and consolidated debt to adjusted consolidated EBITDA, in each case, tested quarterly. At March 31, 2015, Aon plc had no borrowings under, and was in compliance with these financial covenants and all other covenants contained in, the 2017 Facility and 2020 Facility during the three months ended March 31, 2015. Commercial Paper Aon Corporation, a wholly-owned subsidiary of Aon plc, has established a U.S. commercial paper program, which provides for commercial paper to be issued in an aggregate principal amount of up to $900 million, and Aon plc has established a European multi-currency commercial paper program that provides for commercial paper to be issued in an aggregate principal amount of up to €300 million. The U.S. commercial paper program is fully and unconditionally guaranteed by Aon plc and the European commercial paper program is fully and unconditionally guaranteed by Aon Corporation. In the aggregate, the Company had $355 million and $168 million of commercial paper outstanding at March 31, 2015 and December 31, 2014, respectively, which was included in Short-term debt and current portion of long-term debt in the Company's Condensed Consolidated Statements of Financial Position. The weighted average commercial paper outstanding for the three months ended March 31, 2015 was $317 million. The weighted average interest rate of the commercial paper outstanding for the three months ended March 31, 2015 was 0.50%.

Debt

Revolving Credit Facilities

As of December 31, 2014, Aon plc had two primary committed credit facilities outstanding: its $400 million U.S. credit facility expiring in March 2017 (the "2017 Facility") and its €650 million ($707 million based on exchange rates at March 31, 2015) European credit facility expiring in October 2015 (the "2015 Facility"). Aon Corporation entered into the 2015 Facility on October 15, 2010 (Aon plc became a borrower under such facility on April 29, 2013) and Aon plc entered into the 2017 Facility on March 20, 2012. On February 2, 2015, Aon plc replaced the 2015 Facility with a new $900 million multi-currency U.S. credit facility expiring in February 2020 (the "2020 Facility"). Each of these facilities included customary representations, warranties and covenants, including financial covenants that require Aon plc to maintain specified ratios of adjusted consolidated EBITDA to consolidated interest expense and consolidated debt to adjusted consolidated EBITDA, in each case, tested quarterly. At March 31, 2015, Aon plc had no borrowings under, and was in compliance with these financial covenants and all other covenants contained in, the 2017 Facility and 2020 Facility during the three months ended March 31, 2015.

Commercial Paper

Aon Corporation, a wholly-owned subsidiary of Aon plc, has established a U.S. commercial paper program, which provides for commercial paper to be issued in an aggregate principal amount of up to $900 million, and Aon plc has established a European multi-currency commercial paper program that provides for commercial paper to be issued in an aggregate principal amount of up to €300 million. The U.S. commercial paper program is fully and unconditionally guaranteed by Aon plc and the European commercial paper program is fully and unconditionally guaranteed by Aon Corporation. In the aggregate, the Company had $355 million and $168 million of commercial paper outstanding at March 31, 2015 and December 31, 2014, respectively, which was included in Short-term debt and current portion of long-term debt in the Company's Condensed Consolidated Statements of Financial Position. The weighted average commercial paper outstanding for the three months ended March 31, 2015 was $317 million. The weighted average interest rate of the commercial paper outstanding for the three months ended March 31, 2015 was 0.50%.