From the Document, "The United States and Russia signed the New START Treaty [Strategic Arms Reduction Treaty] on April 8, 2010. After more than 20 hearings, the U.S. Senate gave its advice and consent to ratification on December 22, 2010, by a vote of 71-26. Both houses of the Russian parliament--the Duma and Federation Council-- approved the treaty in late January 2011, and it entered into force on February 5, 2011, after Secretary of State Clinton and Foreign Minister Lavrov exchanged the instruments of ratification. Reductions were to be implemented by February 5, 2018, a goal met by both parties. The Treaty is due to expire in February 2021, unless both parties agree to extend it for up to five years."
CRS Report for Congress, R41219
Congressional Research Service: https://crsreports.congress.gov/