Net Income Per Operating Partnership Unit - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income	$ 67,769		$ 48,059		$ 117,917	$ 106,228
Income from discontinued operations	0		0		16,216	0
Net income - basic and diluted	$ 67,769	$ 66,364	$ 48,059	$ 58,169	$ 134,133	$ 106,228
Denominator:
Effect of dilutive shares for diluted net income per Operating Partnership unit (in shares)	196,839		191,905		228,087	176,342
MGP Operating Partnership
Numerator:
Net income	$ 67,769		$ 48,059		$ 117,917	$ 106,228
Income from discontinued operations	0		0		16,216	0
Net income - basic and diluted	$ 67,769	$ 66,364	$ 48,059	$ 58,169	$ 134,133	$ 106,228
Denominator:
Weighted average Operating Partnership units outstanding - basic (in shares)	290,714,102		266,127,214		289,537,067	266,116,366
Effect of dilutive shares for diluted net income per Operating Partnership unit (in shares)	196,839		191,905		228,087	176,342
Weighted average Operating Partnership units outstanding - diluted (in shares)	290,910,941		266,319,119		289,765,154	266,292,708