The shipment was a secret until The Wall Street Journal broke the story on August 2. Since then, Republicans from Donald Trump to Paul Ryan have assailed the White House for paying a gigantic ransom when government-paid ransom is barred under U.S. law, and for hiding the ploy from a public already highly skeptical of the U.S.-Iran nuclear agreement. President Obama denied the payment to Tehran was a ransom. The White House contends the payment simply settled a decades-long financial dispute, and that the settlement was fully disclosed in January—although at the time, officials made no mention that the $400 million arrived in Iran the same as the hostages were freed, a confluence of events bound to arouse suspicion."

http://fortune.com/2016/08/05/money-america-iran/

(http://www.autoadmit.com/thread.php?thread_id=4016183&forum_id=2#36479611)

"So instead, the U.S. negotiators convinced Iran to move the dispute from arbitration to a private settlement. The two sides reached an agreement in mid-2015, at the same time as the U.S. and Iran reached a comprehensive pact on curtailing Iran’s development of nuclear weapons. The financial deal called for the U.S. to refund $1.7 billion to Tehran, consisting of the original $400 million contract for military equipment, plus $1.3 billion in interest."

(http://www.autoadmit.com/thread.php?thread_id=4016183&forum_id=2#36479656)