DETROIT — Detroit’s biggest seller of luxury vehicles isn’t Cadillac anymore. It’s GMC.

GMC’s high-end Denali and AT4 lines are outselling General Motors’ traditional luxury brand in the U.S. this year, according to figures from GM and the Automotive News Data Center. The automaker is building on Denali’s ability to command luxury prices by expanding the AT4 off-road subbrand and planning a pair of high-performance electric vehicles that will revive the Hummer name.

“People are coming in writing $80,000 to $90,000 checks for these trucks,” said Inder Dosanjh, dealer principal at Dublin Buick-GMC and Fremont Buick-GMC in the San Francisco Bay area. “There’s so much demand out there.”

In a year when U.S. auto sales are down 18 percent, most Denalis and AT4s arrive at Dosanjh’s dealerships already sold, and customers are willing to open their wallets during a recession to load them up with extra features.

“We can’t get enough of them,” said Will Churchill, dealer principal at Frank Kent Country in Corsicana, Texas.

Largely because of the success of Denali and AT4, GMC has contributed hefty profits to GM’s bottom line during the coronavirus pandemic and is positioned to generate a sizable portion of the cash cushion needed for the automaker’s $20 billion push into EVs and autonomous driving.

Denali and AT4 have accounted for 40 percent of GMC’s retail sales in 2020 so far and soon could generate as much as half of the brand’s volume, said Duncan Aldred, vice president of global Buick and GMC.

Together, the two subbrands drove GMC to its highest retail market share in the first half of the year since 2005, Aldred said, with an average transaction price 30 percent higher than the industry overall. Buyers paid an average of $57,218