The stakes are big. St. Luke's is the largest non-governmental employer in Idaho; Saint Alphonsus, the fourth largest.
Saint Alphonsus says if the purchase goes through as planned, admissions to its Nampa hospital would drop dramatically because patients would automatically be referred to the St. Luke's hospital in Meridian.
Saint Alphonsus on Monday was among plaintiffs behind an antitrust lawsuit meant to halt Boise-based St. Luke's Nampa expansion plans.
In U.S. District Court, Saint Alphonsus argued St. Luke's acquisition of Saltzer's facility in Nampa threatens to monopolize a broad series of markets in Idaho, increasing costs, reducing quality - and crippling Saint Alphonsus' Nampa hospital.
"It impacts the average every day person in Nampa because it limits patient choice," said Saint Alphonsus spokesperson Elizabeth Duncan.
Saint Alphonsus says the move would give St. Luke's more than 65 percent ownership of primary care physicians in Nampa, driving up costs by crippling fair competition.
St. Luke's spokesperson Ken Dey says Saint Alphonsus is flat out wrong.
"We expect it'll actually lead to more access for patients," he told KBOI 2 News. "We're able to take on overhead costs, and some of the difficulties, so all these doctors can do what they do best -- treat patients. We do not have a policy at St. Luke's where our doctors automatically refer patients to our facilities."
Dey says the transaction, initiated by Saltzer, could wrap up by the end of the year.
Federal and state regulators have already been scrutinizing St. Luke's advances toward Saltzer.