Organization - Narrative (Details)	9 Months Ended	12 Months Ended	29 Months Ended	33 Months Ended	42 Months Ended	72 Months Ended
	Sep. 30, 2016 USD ($) property shares	Dec. 31, 2015 USD ($) shares	Sep. 30, 2016 USD ($) property shares	Dec. 31, 2015 USD ($) shares	Sep. 30, 2016 USD ($) property shares	Dec. 31, 2014 USD ($) offering shares	Sep. 22, 2015 USD ($)	May 07, 2014 USD ($)	Aug. 29, 2008 USD ($)
Subsidiary, Sale of Stock [Line Items]
Agreement term	1 year
Renewal period term	1 year
Number of public offerings | offering						2
Number of shares outstanding (in shares) | shares	175,945,568	175,184,519	175,945,568	175,184,519	175,945,568
Common stock subject to redemption	$ 11,600,000	$ 6,300,000	$ 11,600,000	$ 6,300,000	$ 11,600,000
Limited partnership, purchase price									$ 200,000
Initial capital contribution									$ 1,000
General partner percentage interest obtained									1.00%
Limited partnership, Company's ownership interest (percent)	96.00%
Number of properties contributed | property	5		5		5
Limited Partnership number of units redeemed | shares	0	0
Advisor
Subsidiary, Sale of Stock [Line Items]
Limited liability partnership percentage of interest held (percent)									99.00%
Sponsor and Affiliates
Subsidiary, Sale of Stock [Line Items]
Limited liability partnership percentage of interest held (percent)	2.00%		2.00%		2.00%
Third parties
Subsidiary, Sale of Stock [Line Items]
Limited liability partnership percentage of interest held (percent)	2.00%		2.00%		2.00%
Common Stock | Share Redemption Program
Subsidiary, Sale of Stock [Line Items]
Value of shares redeemed	$ 47,200,000			17,300,000	$ 47,200,000
Stock redeemed during period (in shares) | shares					4,768,238
Sale to Public
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares) | shares						126,592,885
Private Offering
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of private placement	$ 1,400,000,000					$ 1,300,000,000
Common stock issued (shares) | shares	180,713,806		180,713,806		180,713,806
2014 Distribution Reinvestment Plan Offering
Subsidiary, Sale of Stock [Line Items]
Value of shares to be registered								$ 75,000,000.0
Distribution Reinvestment Plan
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares) | shares			12,353,953
Value of shares to be registered							$ 100,000,000.0
Gross proceeds from issuance of shares			$ 126,500,000
Equity offering, termination notice period			10 days
Common stock issued	$ 149,500,000	$ 110,200,000	$ 149,500,000	$ 110,200,000	$ 149,500,000