Was the New Deal a new idea or did Roosevelt reuse old ideas?
The New Deal was not a completely new idea. What was new was that the government was willing to do all of these new things and to do them all at the same time.
The New Deal came out of the minds of a "brain trust" that President Roosevelt had assembled. They brought to the table many ideas that had been used or had been floated before. Some ideas, like some for the NRA, came from the time of WWI. Other ideas, like the TVA, had been proposed earlier in the century but had not been acted upon.
The idea of having the government put people to work was not new. What was new was actually having the government do so on a large scale in the United States.