Organization and Business - Schedule of Issuance and Sale of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended								12 Months Ended
	Jul. 31, 2017	Mar. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common shares sold (in shares)	21,500,000	17,250,000
Net proceeds from issuance of common stock (approximately)	$ 420,700	$ 300,800
2016 ATM Program | ATM Program | Operating Partnership
Class of Stock [Line Items]
Common shares sold (in shares)			2,197,914	0	4,150,000	0	135,531	0	0	0	6,347,914	135,531
Weighted average price (in dollars per share)			$ 18.39	$ 0	$ 20.07	$ 0	$ 19.09	$ 0	$ 0	$ 0	$ 19.48	$ 19.09
Net proceeds from issuance of common stock (approximately)			$ 40,011	$ 0	$ 82,440	$ 0	$ 2,561	$ 0	$ 0	$ 0	$ 122,451	$ 2,561