The main purpose of this study is to examine the combination of the two drugs, Ofatumumab and Idelalisib, in participants who have been diagnosed with CLL/SLL and have not previously received treatment but do require treatment. The investigators hope to observe how participants' disease will be impacted by this treatment and whether they will benefit more from combining these drugs together rather than taking them separately. Both of these drugs have been used in treatment for CLL / SLL and information from those research studies suggests that these drugs may help patients with CLL/SLL.