Inclusion Criteria:

          -  Histologically confirmed FL.

          -  Documented CD20+ FL.

          -  Relapsed or refractory to any prior rituximab-containing regimen.

          -  Previously treated with a maximum of 4 cancer-directed treatment regimens.

          -  At least 1 measurable lesion > 1.5 cm in at least 1 dimension by computed tomography
             or magnetic resonance imaging.

          -  Must be willing to undergo an incisional or excisional lymph node biopsy of accessible
             adenopathy or provide the most recent, available archived tumor biopsy.

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.

        Exclusion Criteria:

          -  Clinical evidence of transformation to a more aggressive subtype of lymphoma or Grade
             3B FL.

          -  History of central nervous system lymphoma (either primary or metastatic).

          -  Allogeneic stem cell transplant within the last 6 months, or active graft-versus-host
             disease following allogeneic transplant or autologous stem cell transplant within the
             last 3 months before the date of the first dose of study drug administration.

          -  Use of any potent cytochrome P450 3A4 inhibitors or inducers within 14 days or 5
             half-lives (whichever is longer) before the first dose of study drug.

          -  Prior treatment with a selective PI3Kδ inhibitor or a pan PI3K inhibitor.

          -  Prior treatment with bendamustine (within 12 months of the start of study treatment).
             Subjects with prior bendamustine treatment (> 12 months before the start of study
             treatment) are eligible if they meet the following criteria:

               -  Did not discontinue because of tolerability concerns.

               -  Achieved either partial or CR to the bendamustine regimen of at least 12 months
                  in duration before relapse/progression.

               -  Experienced progression following a regimen containing an alkylating agent.

          -  Received prior obinutuzumab.

          -  Received rituximab within 4 weeks of study start.

          -  Prior treatment-related toxicities that have not resolved to ≤ Grade 1 before the date
             of study drug administration except for stable chronic toxicities (≤ Grade 2) not
             expected to resolve (eg, stable Grade 2 peripheral neurotoxicity).

          -  Received any prior monoclonal antibody (except an anti-CD20 antibody) within 90 days
             before the date of study start.

          -  History of severe allergic or anaphylactic reactions to monoclonal antibody therapy
             (eg, subjects in whom re-administration with rituximab would be contraindicated for
             safety reasons).