Debt MIF Warehousing Agreement (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Line of Credit Facility [Line Items]
Maximum Borrowing Availability under all Credit Lines	$ 200,000	$ 185,000
Notes payable bank - financial services operations	168,195	$ 152,895
Warehousing Agreement - First Amendment to Second Amended and Restated [Member]
Line of Credit Facility [Line Items]
M/I Financial Maximum Borrowing Capacity	125,000
M/I Financial Temporary Increase Maximum Borrowing Capacity	$ 150,000
LIBOR basis points	237.5
Debt Instrument, Basis Spread on Variable Rate	2.75%
Repurchase Agreement - Amendment No. 4 [Member]
Line of Credit Facility [Line Items]
M/I Financial Maximum Borrowing Capacity	$ 35,000
M/I Financial Temporary Increase Maximum Borrowing Capacity	$ 50,000
Minimum [Member] | Repurchase Agreement - Amendment No. 4 [Member]
Line of Credit Facility [Line Items]
LIBOR basis points	250
Maximum [Member] | Repurchase Agreement - Amendment No. 4 [Member]
Line of Credit Facility [Line Items]
LIBOR basis points	275