Taxis and are Ubers available and are approximately $15-$20 dollars to the Reston, VA hotels
From Dulles Internation Airport to Hyatt Regency (directly from Hyatt's website):
"Our hotel offers a complimentary shuttle to and from Dulles Airport.
Text the keyword “SHUTTLE” to 703-991-2117 when you arrive at the airport. The requested pick up times will be at the top of each hour between 6 a.m. to 10 p.m. Monday through Friday, and 7:00 a.m. to 10:00 p.m. on Saturday and Sunday. Requests for pick should be received at least 15 minutes prior to the top of hour. The pick-up and drop-off point will be at curbs 2A and 2H, adjacent to the lower level baggage claim level.
Return shuttle transportation from the hotel departs 45 minutes past the hour, beginning at 5:45 a.m. Monday through Friday, and 6:45 a.m. Saturday and Sunday."