ARM II: Patients receive nivolumab IV over 60 minutes and ipilimumab IV over 90 minutes once every 3 weeks for 12 weeks. Patients then receive nivolumab IV over 60 minutes every 2 weeks. Courses repeat every 42 days for up to 2 years in the absence of disease progression or unacceptable toxicity. Patients who progress by imaging during the first 12 weeks of therapy may continue treatment, at the discretion of the patient and treating investigator.