Discount brokerage Scottrade is being acquired by rival TD Ameritrade in a $4 billion deal. The companies announced the deal early Monday, following several weeks of news reports about the merger. The sale is subject to regulatory approvals, and is slated to close by Sept. 30, 2017. Scottrade will convert to TD Ameritrade systems in 2018. Combined, the two companies have $944 billion in total client assets and 10 million funded client accounts. "It gives us a lot of power to combine the two," Scottrade's founder and CEO Rodger Riney told the Post-Dispatch Monday. "It is a business that has...