You can read the story in the Washington Post here:
For the record, technically, both the Washington Post and the Obama White House seem to have their facts a bit wrong. The governor did not expand Medicaid per se. He took a separate program that was slated to expire at the end of 2013 and dropped the new Obamacare provisions and coverage into that.
Here is another story on this from the Omaha World-Herald:
Iowa Gov. Branstad reaches deal on expanding health care for poor