WASHINGTON (Reuters) - The Republican and Democratic leaders of the U.S. Senate Judiciary Committee asked Attorney General Jeff Sessions and FBI Director James Comey on Wednesday to send the committee documents and provide a briefing on the resignation of President Donald Trump’s national security adviser. Citing reports that both the Federal Bureau of Investigation and Justice Department were involved in events leading to Michael Flynn’s departure, Senators Chuck Grassley and Dianne Feinstein said they raised “substantial questions” about Flynn’s discussion with Russian officials. 