Gay workers are for the first time protected at all 100 firms on Fortune's Best Companies To Work For list, reported.

In 2008, 95 of the companies on the financial glossy's top 100 list included non-discrimination policies that include sexual orientation. That number had risen to 99 by 2011.

“It's been gathering strength over the 15 years that we've done the survey,” Milton Moskowitz, a co-author of the list, told CNN.

Michael Cole-Schwartz, communications manager at the Human Rights Campaign (HRC), the nation's largest gay rights advocate, said he wasn't surprised by the unanimous support.

“It's not surprising to me that the places that are ranked the best to work are also the ones that are going to respect and value their employees,” Cole-Schwartz said. “The evolution is clearly in the direction of equality in the workplace.”

Roughly 86% of Fortune 500 companies have a similar policy in place, according to data from the HRC.

Eighty-nine of the 100 companies listed on the Best Companies To Work For list also provide benefits to the domestic partners of gay workers.

(Related: Microsoft, Nike endorse gay marriage in Washington.)