We live and work in Boston, Massachusetts. I work for Company A in computers and my wife for Company B in medicine, both of us with clauses for intellectual property ownership in our employment contracts. Hypothetically, if I had a medical patent idea generated solely by me, would I need to take any precautions before discussing it with my wife to avoid giving her employer any claims to it? Or are there general protections because we're married?
There is a difference between "idea" and "invention". Only an invention is subject to being patented, thus becoming an enforceable property right. Disclosing ideas, without restrictions, can quickly mean you lose any control over resulting inventions. No, marriage does not automatically imply ownership of ideas of the spouse, let alone inventorship.
Hypothetically, under US law, each inventor must file an oath and declaration regarding inventorship of the invention disclosed and claimed in the application for a patent. Where an inventor has a legal obligation to the employer to cooperate in such things, but refuses, there are other ways to file a substitute.
However, where the inventor is independent, the employer has no inherent ownership claim and the inventor has no obligation to sign anything.
If, on the other hand, the "idea" is prematurely disclosed to others, outside of fiduciary or other obligations of confidentiality, such others could proceed to make their own invention, using their own inventors, and file and claim the patent advantages of that invention without regard to where they obtained the initial idea.
One major goal of the patent system is to reward the disclosure of "new and useful" inventions to the public (in the form of a patent application), in exchange for a "limited right" of the inventors to reap the financial advantages, once the invention is deemed patentable. Under current laws, the "first to file" a claim to the invention is presumed to be "the inventor".
A less wooly analysis might be had from experts in the Ask Patents area of this site.