Equity - Additional Information (Detail) - $ / shares |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Equity [Line Items] | |||
| Capital stock, shares authorized | 100,000,000 | ||
| Common stock, shares authorized | 80,000,000 | 80,000,000 | |
| Common stock, par value | $ 0.001 | $ 0.001 | |
| Preferred stock, shares authorized | 20,000,000 | 20,000,000 | |
| Preferred stock, par value | $ 0.001 | $ 0.001 | |
| Common stock, voting rights | one vote per share | ||
| Preferred stock, shares issued | 0 | 0 | |
| Preferred stock, shares outstanding | 0 | 0 | |
| Description of total shares quarterly redeemed | Total shares redeemed pursuant to the Share Redemption Program in any quarter may not exceed 1% of the total number of shares outstanding at the beginning of the calendar year plus 50% of the total number of any additional shares issued during the prior calendar quarter under the Corporation’s Distribution Reinvestment Plan (“DRIP”), provided that the total number of shares redeemed during any calendar year may not exceed 5% of the number of shares outstanding as of the first day of such calendar year. | ||
| Common stock, shares issued | 18,909,000 | 15,158,000 | |
| Distribution Reinvestment Plan | |||
| Equity [Line Items] | |||
| Percentage of shares in value offered | 98.00% | ||
| Common stock, shares issued | 1,592,000 | 1,076,000 | 684,000 |
| Stock Redeemable After 12 Months but Less than Five Years | |||
| Equity [Line Items] | |||
| Share value redeemable percentage | 95.00% | ||
| Stock Redeemable after Five Years | |||
| Equity [Line Items] | |||
| Share value redeemable percentage | 100.00% |