Noncontrolling Interests - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) Entity Property shares	Dec. 31, 2018 USD ($) shares	Sep. 30, 2017 Property
Noncontrolling Interest [Line Items]
Number of third-party joint venture partners | Entity	6
Number of properties	167
Common OP units
Noncontrolling Interest [Line Items]
Conversion of common units to common stock (in shares) | shares	126,313	412,343
Preferred OP Unit Member [Member]
Noncontrolling Interest [Line Items]
Conversion of common units to common stock (in shares) | shares	42,271
Three off-campus properties | AMERICAN CAMPUS COMMUNITIES OPERATING PARTNERSHIP LP
Noncontrolling Interest [Line Items]
Number of third-party joint venture partners | Entity	4
In-process development properties
Noncontrolling Interest [Line Items]
Number of properties			3
In-process development properties | Three off-campus properties
Noncontrolling Interest [Line Items]
Number of properties	10
Core Transaction
Noncontrolling Interest [Line Items]
Number of third-party joint venture partners	1
Number of properties	3		2
Noncontrolling interest, change in redemption Value | $	$ 11.8	$ 68.7
Purchase of noncontrolling interests | $	$ (88.3)
Operating Partnership [Member] | AMERICAN CAMPUS COMMUNITIES OPERATING PARTNERSHIP LP
Noncontrolling Interest [Line Items]
Equity interests held by owners of common units and series A preferred units/ retained by seller (percent)	0.40%	0.50%