The 27-year-old Slade will join his All Blacks team mate Conrad Smith at the ambitious French club, who have been promoted to the French top level for next season.
“It certainly wasn't easy. I have lost a lot of sleep over it,” Slade told The Press newspaper in Christchurch. “But it is not just a rugby decision, a lifestyle decision or a financial decision.
“It is a combination of all three and with the stage of where I am in my life and my career, my wife and I have always wanted to do a bit of travel as well.”
Local media have reported his contract was worth in excess of NZ$700,000 ($521,990) a season, something New Zealand Rugby would have struggled to match, though Slade said their offer had been competitive.
“They did everything they could to keep me here, I certainly wasn't discouraged by the package they put together,” he added.
Slade, who has played 17 tests for the All Blacks, has been earmarked as a potential utility player for the World Cup squad with his ability to play flyhalf and fullback, while he also appeared on the wing in a test last year.
He joins a large number of All Blacks leaving New Zealand at the conclusion of the tournament in England, with Dan Carter, Smith, Ma'a Nonu, Ben Franks and Charles Piutau already confirmed with contracts in Europe.
Captain Richie McCaw, loosehead prop Tony Woodcock and hooker Keven Mealamu are also expected to retire.
Slade's departure from the Canterbury Crusaders will also spark a crisis at flyhalf for the seven-times Super Rugby champions next season.
Carter and three-test All Black Tom Taylor have also already said they would take up European club contracts next season, while Tyler Bleyendaal left for Munster at the end of last season. – Reuters
Original source: Slade joins All Blacks exodus