These 3 Stocks Doubled in 2017 — Are They Still Buys?

Sir Isaac Newton may be best known for his first law of motion, which states in part that "an object in motion tends to stay in motion unless acted upon by an outside force." The same can be said for certain stocks. Each of the companies discussed here gained more than 100% last year, and investors will rightly be asking themselves if they will continue to gain ground, given their massive outperformance last year, or if they're headed for a fall.