v3.8.0.1

Consolidated Statement of Stockholders' Equity (Parenthetical) - $ / shares | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Issuance of membership units, number of units | 161,000 | 97,000 | 793,000
Redemption of shares of common stock, shares | 119,000 | 109,000 | 43,000
Number of membership units exchanged | 37,000 | 0 | 0
Common Stock |  |  |
Issuance of shares of common stock, shares | 3,833,000 | 3,784,000 | 4,535,000
Redemption of shares of common stock, shares | 119,000 | 109,000 | 43,000
Cancellation shares of common stock, shares |  |  | 14,000
Issuance of shares common stock upon conversion of membership units | 37,000 |  |

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