Organization and Business - Narrative - Public Offering (Details) - USD ($)				3 Months Ended								12 Months Ended		41 Months Ended	108 Months Ended
	May 02, 2018	Mar. 20, 2018	Mar. 13, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 20, 2013	Dec. 31, 2017	Mar. 13, 2019	May 09, 2018	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 10, 2012	Jul. 19, 2010	Jul. 23, 2009
Class of Stock [Line Items]
Common stock, estimated value, per share (in dollars per share)																	$ 9.84
Distributions declared per common share (in dollars per share)				$ 0.140	$ 0.140	$ 1.153	$ 0.177	$ 0.181	$ 0.181	$ 0.179	$ 0.177	$ 1.610	$ 0.718
Common share, distribution rate per share per day, declared (in dollars per share)			$ 0.00151890410958904		0.001519	0.001683	0.001964
Stock issued during period, dividend reinvestment plan (in shares)															4,073,759
Proceeds from issuance of common stock, dividend reinvestment plan															$ 39,580,847
Public Offering [Member]
Class of Stock [Line Items]
Stock issued during period, shares, new issues (in shares)														76,095,116
Proceeds from issuance of common stock														$ 769,573,363
Distribution Reinvestment Plan [Member]
Class of Stock [Line Items]
Share price (in dollars per share)																					$ 9.73		$ 9.5
Stock issued during period, dividend reinvestment plan (in shares)														4,073,759
Proceeds from issuance of common stock, dividend reinvestment plan														$ 39,580,847
Common Stock [Member]
Class of Stock [Line Items]
Share price (in dollars per share)			$ 9.24	$ 9.24		$ 10.24	10.24					$ 9.24
Common stock, estimated value, per share (in dollars per share)								$ 10.84					$ 10.84		$ 10.84			$ 11.65	$ 11.44	$ 10.35
Common share, distribution rate per share per day, declared (in dollars per share)					$ 0.001519		$ 0.001964
Common stock, distribution rate, percentage		6.00%			6.00%	6.00%	7.00%
Common Stock [Member] | Primary Offering [Member]
Class of Stock [Line Items]
Common stock, capital shares reserved for future issuance, maximum (in shares)																						150,000,000
Share price (in dollars per share)																						$ 10
Common Stock [Member] | Public Offering [Member]
Class of Stock [Line Items]
Common stock, capital shares reserved for future issuance, distribution reinvestment plan, up to (in shares)																						15,789,474
Share price, distribution reinvestment plan (in dollars per share)																						$ 9.5
Dividend Paid [Member]
Class of Stock [Line Items]
Distributions declared per common share (in dollars per share)	$ 1.00
Subsequent Event [Member]
Class of Stock [Line Items]
Share price (in dollars per share)																$ 9.40349170419484
Subsequent Event [Member] | Common Stock [Member]
Class of Stock [Line Items]
Common stock, estimated value, per share (in dollars per share)																$ 9.40