Common Stock/Partners' Capital - Additional Information (Detail) shares in Thousands, $ in Thousands		9 Months Ended
	May 01, 2017 USD ($) shares	Sep. 30, 2018 Partner shares	Sep. 30, 2017 USD ($) shares	Dec. 31, 2017 shares
Class of Stock [Line Items]
Common stock, shares issued		364,858		364,424
Proceeds from sale of common shares / units, net of offering costs | $			$ 548,055
MPT Operating Partnership, L.P. [Member]
Class of Stock [Line Items]
Proceeds from sale of common shares / units, net of offering costs | $			$ 548,055
Ownership interest in equity		99.92%
Number of other partners | Partner		2
Number of units sold			43,100
Public Offering [Member]
Class of Stock [Line Items]
Common stock, shares issued	43,100
Additional shares purchased by underwriters	5,600
Proceeds from sale of common shares / units, net of offering costs | $	$ 548,000