Expand and Fill the missing dates with last not null value

Input and Expected Output:

Data Setup:

create table tx_data(dt date, amnt number);

insert into tx_data values(to_date('20-JUL-2019','DD-MON-YYYY'),100);
insert into tx_data values(to_date('25-JUL-2019','DD-MON-YYYY'),200);
insert into tx_data values(to_date('30-JUL-2019','DD-MON-YYYY'),300);

commit;

Query:

with d1 as (
select min(dt) mi,max(dt) mx, max(dt)-min(dt) num
from tx_data),
dt_range as (select level-1+mi dt
from d1
connect by level <=num+1)
select dt_range.dt,
       last_value(amnt ignore nulls) over(order by dt_range.dt) amnt
from dt_range left outer join tx_data
on (dt_range.dt = tx_data.dt)

order by 1;