MANKATO, Minn. -- Two-and-a-half years ago, Mike Zimmer was debating whether he should take a second interview with the Minnesota Vikings and risk another round of rejection in his ongoing quest to be an NFL head coach.On Thursday, Zimmer began his third training camp with the Vikings knowing the team plans to invest in him for years to come.The Vikings kicked off training camp Thursday by announcing they had signed their head coach to a contract extension, rewarding Zimmer for leading the team to its first NFC North championship in six years. Terms of the deal were not disclosed, but general manager Rick Spielman said, There is no doubt that Coach Zimmer is going to be our football coach here for a long time.The team approached Zimmers agent, Marvin Demoff, about a new contract this spring, intent on rewarding the coach whose exacting style helped the Vikings become the first team ever to host a playoff game in a temporary stadium last year. Zimmer was not headed into the final year of his current deal, so the Vikings didnt have any urgency to complete the deal from a contractual standpoint. Nonetheless, the team, which moves into its new $1.1 billion stadium this fall, also appears to have its football foundation in place.Im extremely grateful to the Wilfs and to Rick, Zimmer said. They kind of came to us and wanted to get it done. They really didnt have to; there was nothing that was pushing this deal. I feel very, very fortunate to be the coach of the Vikings. Its a great organization with a lot of great people. Theres no way we could have had the success that weve had to this point without the people in the front office, the people in the business (side) and all those things. Its good to get it done now and have a chance to move forward.Zimmer became a head coach for the first time at 58 years old, and didnt seem to betray any sense of relaxation now that the deal is finished.Thats what pushes me, is that someone else can come and take my job if we dont play as good as we can play, he said. Proving people wrong, thats just my mentality.Zimmer, who is 18-14 in two seasons at the Vikings helm, led Minnesota last season to its first NFC North division title since 2009 before the team exi