Diluted earnings per share increased 19% to $1.95. Finally, capital expenditures and capitalized software totaled $18 million, and cash flow from operations rose to $180 million in the second quarter.
Turning to Slide 6. You can see the revenue and expense components of our second quarter results. Futures revenues rose 14% to a record $169 million on record volume and ICE Futures Europe.
OTC energy revenue decreased 3% to $101 million, while OTC credit revenue declined at $36 million.
Taken together, our consolidated transaction in clearing revenues increased 6% to $307 million.
Market data revenue grew 21% to a record $37 million, demonstrating continued demand for our globally relevant commodity market and related market data services.
ICE's second quarter consolidated expenses are summarized on the right side of Slide 6. Operating expenses were $136 million, up just 1% from the prior year and down from the first quarter. Our disciplined expense management, coupled with solid top line growth, drove our operating margins to 61% compared to 59% in the last year's second quarter.
During the second quarter, comp and benefits expense rose 4%, and we recorded $4 million of acquisition-related expense.
We expect ongoing M&A expenses of $1 million to $2 million per quarter as we continue to evaluate a range of strategic M&A opportunity. And we continue to forecast full-year expense growth in the range of 3% to 6%, which we believe will enable investment in key growth opportunities, operating efficiency and solid earnings growth.
Next on Slide 7, I will highlight the record performance of our Futures segment during the second quarter.
Record revenue was driven by record average daily volume of 1.6 million contracts, up 11% year-to-year. ICE Futures Europe and ICE Futures U.S. posted record revenue in the quarter. This strong performance was once again led by our Brent Crude contract, which despite prices declining more than 20% during the second quarter, while volumes rise nearly 30%, as it's ascendant as the global benchmark continues.