Bit of a silly question. I live where the 4g signal is poor. While at home I keep the data turned off so why is the idle still high (59% as of this posting)? (wifi connection is strong)
Verizon's VoLTE is called "Advanced Calling." Try turning it off as discussed here.
Low to low-medium signal could certainly contribute to Cell Standby battery usage, although I agree that 59% is pretty excessive.
I'm just speculating here, but I would guess that if you have Advanced Calling on, then the phone would always be trying to latch onto an LTE signal, even if your mobile data is turned off. So if you turn off Advanced Calling, perhaps the phone won't expend as much energy trying to maintain the LTE signal -- but this assumes the 3G signal is better, and I'm not sure if that would be the case.
Even if your wi-fi is on, the phone will keep trying to maintain the cell signal unless you have Airplane Mode turned on.