Key Inclusion Criteria:

          1. Patients with histologically or cytologically documented squamous or non-squamous
             NSCLC with stage IIIB or stage IV disease, who received no prior systemic treatment
             for recurrent or metastatic NSCLC

          2. Availability of an archival (≤5 months) or on-study obtained formalin-fixed,
             paraffin-embedded tumor tissue sample which has not previously been irradiated

          3. Expression of PD-L1 in ≥50% of tumor cells determined by the commercially available
             assay performed by the central laboratory

          4. At least 1 radiographically measureable lesion by computed tomography (CT) or magnetic
             resonance imaging (MRI) per RECIST 1.1 criteria. Target lesions may be located in a
             previously irradiated field if there is documented (radiographic) disease progression
             in that site

          5. Eastern Cooperative Oncology Group (ECOG) performance status of ≤1

          6. Anticipated life expectancy of at least 3 months

        Key Exclusion Criteria:

          1. Patients who have never smoked, defined as smoking ≤100 cigarettes in a lifetime

          2. Active or untreated brain metastases or spinal cord compression

          3. Patients with tumors tested positive for Epidermal growth factor receptor (EGFR) gene
             mutations, Anaplastic lymphoma kinase (ALK) gene translocations, or C-ros oncogene
             receptor tyrosine kinase(ROS1) fusions

          4. Encephalitis, meningitis, or uncontrolled seizures in the year prior to informed
             consent

          5. History of interstitial lung disease (eg, idiopathic pulmonary fibrosis or organizing
             pneumonia), of active, noninfectious pneumonitis that required immune-suppressive
             doses of glucocorticoids to assist with management, or of pneumonitis within the last
             5 years

          6. Ongoing or recent evidence of significant autoimmune disease that required treatment
             with systemic immunosuppressive treatments, which may suggest risk of immune-related
             treatment-emergent adverse events (irTEAEs)

          7. Previous treatment with idelalisib at any time (ZYDELIG®)

          8. Patients with a condition requiring corticosteroid therapy (>10 mg prednisone/day or
             equivalent) within 14 days of randomization

        Note: Other protocol defined Inclusion/Exclusion criteria may apply