A Study of Idasanutlin in Combination With Obinutuzumab in Relapsed/Refractory (R/R) Follicular Lymphoma (FL) and in Combination With Rituximab in R/R Diffuse Large B-Cell Lymphoma (DLBCL) Participants

Inclusion Criteria: * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 * Histologically documented cluster of differentiation (CD) 20-positive B-cell lymphoma classified as relapsed or refractory FL or DLBCL after treatment with at least two prior chemoimmunotherapy regimens that included an anti-CD20 monoclonal antibody (mAb) and for which no other more appropriate treatment option exists * At least one bidimensionally measurable lesion * Agreement to remain abstinent or use adequate contraception, among women or men of childbearing potential Exclusion Criteria: * Known CD20-negative status at relapse or progression * Prior allogeneic stem cell transplantation (SCT), or autologous SCT within 100 days prior to Day 1 of Cycle 1 * Current use of systemic corticosteroids greater than (\>) 20 mg prednisone per day (or equivalent), or prior anti-cancer therapy to include: radioimmunoconjugate within 12 weeks; mAb or antibody-drug conjugate within 4 weeks; or radiotherapy/chemotherapy/hormone therapy/targeted small-molecule therapy within 2 weeks prior to Day 1 of Cycle 1 * Requirement for chronic anticoagulation * Central nervous system (CNS) disease * Active infection * Positive for human immunodeficiency virus (HIV) or hepatitis B or C * Receipt of a live virus vaccine within 28 days prior to Day 1 of Cycle 1 * Poor hematologic, renal, or hepatic function * Pregnant or lactating women * History of progressive multifocal leukoencephalopathy (PML)