Gregory C. Case
Thanks very much, and good morning, everyone, and welcome to our first quarter conference call. Joining me here today is our CFO, Christa Davies. Consistent with previous quarters, I like to cover 3 areas before turning the call over to Christa for further financial review and would note that there are slides available on our website for you to follow along with our commentary today.
First is our performance against key metrics we communicate to shareholders. Second is overall organic growth performance. And third is continued areas of investment across Aon. On the first topic, our performance versus key metrics. Each quarter, we measure our performance against the 3 metrics we focus on achieving over the course of the year: grow organically, expand margins and increase earnings per share.
Turning to Slide 3, in the first quarter, organic revenue was 4% overall, reflecting the strongest rate of organic revenue growth since the second quarter of 2007 and the strength of our industry-leading platform. Operating margin decreased 80 basis points, driven primarily by significant investments we're making across our businesses to increase long-term growth. Finally, EPS was $0.98, including $0.06 of unfavorable impact from foreign currency.
Overall, our first quarter performance reflects improved organic revenue growth across our businesses as foreign currency movement and significant investments to drive greater long-term growth has an unfavorable impact on bottom line results. While we're not satisfied with margin improvement and working capital management in the near term, we fully anticipate improved performance in the second half of the year are on track with our long-term targets and have completed significant steps to position the firm for long-term growth, strong free cash flow generation and increased financial flexibility, as highlighted by the completed redomestication to London in early April.
Turning to Slide 4, on the second topic of growth, I want to spend the next few minutes discussing the quarter for both our segments. In Risk Solutions, overall organic revenue growth was 4% with growth across every major business. As market-related conditions continue to stabilize, we're driving a set of initiatives that are strengthening underlying performance and positioning our Risk Solutions segment for long-term growth and leverage on improving economy. With management of our renewal book through Client Promise and retention rates of 90% or better on average, highlighting strong client satisfaction.