Related Party Arrangements - Narrative - Refinancing Fees (Details) - Steadfast Income Advisor, LLC [Member] - Advisor and its Affiliates [Member] - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 39,249,788	$ 51,092,503	$ 47,808,767
General and Administrative Expense [Member] | Refinancing Fee [Member]
Related Party Transaction [Line Items]
Percentage of refinancing amount	0.50%
Related party transaction, expenses from transactions with related party	$ 422,160	$ 86,675	$ 3,283,737