Equity - Shares Issued and Gross Proceeds (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Total redemptions (shares)	(1,512,250)
Total shares outstanding (in shares)	77,835,406	77,175,283
Class T
Class of Stock [Line Items]
Total redemptions (shares)
Total shares outstanding (in shares)	84,128	4,148
Class S
Class of Stock [Line Items]
Total redemptions (shares)
Total shares outstanding (in shares)	274	268
Class D
Class of Stock [Line Items]
Total redemptions (shares)
Total shares outstanding (in shares)	16,408	268
Class I
Class of Stock [Line Items]
Total redemptions (shares)
Total shares outstanding (in shares)	405,081	267,476
Class A
Class of Stock [Line Items]
Total redemptions (shares)	(830,715)
Total shares outstanding (in shares)	26,110,337	25,995,943
Class AA
Class of Stock [Line Items]
Total redemptions (shares)	(680,454)
Total shares outstanding (in shares)	50,231,925	49,942,471
Class AAA
Class of Stock [Line Items]
Total redemptions (shares)	(1,081)
Total shares outstanding (in shares)	987,253	964,709
IPO
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 728,754
Common stock, number of shares issued (in shares)	73,157,115
IPO | Class T
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 834
Common stock, number of shares issued (in shares)	83,698
IPO | Class S
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 3
Common stock, number of shares issued (in shares)	264
IPO | Class D
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 157
Common stock, number of shares issued (in shares)	16,330
IPO | Class I
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 3,741
Common stock, number of shares issued (in shares)	392,967
IPO | Class A
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 240,780
Common stock, number of shares issued (in shares)	24,199,760
IPO | Class AA
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 474,858
Common stock, number of shares issued (in shares)	47,562,870
IPO | Class AAA
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 8,381
Common stock, number of shares issued (in shares)	901,226
Distribution Reinvestment Plan
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 52,924
Common stock, number of shares issued (in shares)	5,586,058
Distribution Reinvestment Plan | Class T
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 4
Common stock, number of shares issued (in shares)	430
Distribution Reinvestment Plan | Class S
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 0
Common stock, number of shares issued (in shares)	10
Distribution Reinvestment Plan | Class D
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 1
Common stock, number of shares issued (in shares)	78
Distribution Reinvestment Plan | Class I
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 116
Common stock, number of shares issued (in shares)	12,114
Distribution Reinvestment Plan | Class A
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 23,487
Common stock, number of shares issued (in shares)	2,477,651
Distribution Reinvestment Plan | Class AA
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 28,878
Common stock, number of shares issued (in shares)	3,049,343
Distribution Reinvestment Plan | Class AAA
Class of Stock [Line Items]
Gross proceeds received to date of shares issued	$ 438
Common stock, number of shares issued (in shares)	46,432
Share Distribution
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	568,483
Share Distribution | Class T
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Share Distribution | Class S
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Share Distribution | Class D
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Share Distribution | Class I
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Share Distribution | Class A
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	263,641
Share Distribution | Class AA
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	300,166
Share Distribution | Class AAA
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	4,676
Restricted stock units issued
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	36,000
Restricted stock units issued | Class T
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Restricted stock units issued | Class S
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Restricted stock units issued | Class D
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Restricted stock units issued | Class I
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Restricted stock units issued | Class A
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Restricted stock units issued | Class AA
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	0
Restricted stock units issued | Class AAA
Class of Stock [Line Items]
Common stock, number of shares issued (in shares)	36,000