I have never personally flown out of Detriot so I can't recommend a park and fly hotel but I did find this list that might be of some some use to you. Hope it helps.
Crowne Plaza Hotel, 8000 Merriman, 734-729-2600, $135.07 for one night in a nonsmoking room with a king-size or two double beds and seven days of parking at Qwik Park. Available Thursday through Sunday nights.
Quality Inn, 7600 Merriman, 734-728-2430, $93.87 for one night in a room with a queen-size or two double beds and seven days of parking in a fenced lot at the inn.
Doubletree Detroit Airport, 31500 Wick Road, 734-467-8000, $112.86 on either Friday and Saturday night for a room with a king- or queen-size bed and seven days at Park 'N' Go. The price rises to $135.66 Sunday through Thursday.
Red Roof Inn at Detroit Metro, 7680 Merriman, 734-641-9006, $93.06 for one night in a room with two queen-size beds and seven days at Qwik Park.
Romulus Marriott, 30559 Flynn Road, 734-729-7555, $124.26 for one night in a room with a king-size or two double beds and eight days at Airlines Parking.
Four Points by Sheraton, 8800 Wickham Road, 734-729-9000, $123.17 for one night Friday or Saturday in a room with a king-size or two double beds and seven days of parking on the hotel lot. The price rises to $145.77 Sunday through Thursday.
Detroit Airport Marriott, Detroit Metro Airport, 734-941-9400, $219.90 for a deluxe room with a king-size or two double beds and eight days at Airlines Parking.
I'm sure if you need to park longer than what is listed it can arranged with the hotel when booking.
Good luck and happy planning,
Myst