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Stock Transactions and Unit Redemptions - Additional Information (Detail) - USD ($) |  |  |  | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Mar. 09, 2018 | Dec. 13, 2017 | Apr. 12, 2017 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Aug. 01, 2018 | Mar. 31, 2018
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Payment percentage of the gross proceeds from the sale of shares | 2.00% |  | 2.00% |  |  |  |  |
Aggregate proceeds from issuance of common stock |  |  |  |  |  | $ 327,624,000 |  |
Stock repurchase program and unit redemption remaining authorized amount |  |  |  | $ 249,908,000 |  |  |  |
CF & Co [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Common stock, issued during the period |  |  |  | 200,000 | 900,000 |  |  |
Payment percentage of the gross proceeds from the sale of shares |  | 5.50% |  |  |  |  |  |
Aggregate proceeds from issuance of common stock |  |  |  | $ 900,000 | $ 5,300,000 |  |  |
Weighted-average price per share |  |  |  | $ 4.11 | $ 6.17 |  |  |
Class B Common Stock [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Common stock, issued during the period |  |  |  | 0 | 0 |  |  |
Common stock outstanding |  |  |  | 45,884,000 | 45,884,000 |  |  |
Common stock, shares issued |  |  |  | 45,884,000 | 45,884,000 |  |  |
Common stock value issued |  |  |  | $ 459,000 | $ 459,000 |  |  |
Class A Common Stock [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Common stock, issued during the period |  |  |  | 390,570 | 212,711 | 26,003,424 |  |
Common stock outstanding |  |  |  | 323,018,000 | 307,915,000 |  |  |
Common stock, shares issued |  |  |  | 373,545,000 | 358,440,000 |  |  |
Common stock value issued |  |  |  | $ 3,735,000 | $ 3,584,000 |  |  |
Company's repurchase and additional redemption authority amount |  |  |  |  |  |  | $ 300,000,000.0 |
Stock repurchase program and unit redemption remaining authorized amount |  |  |  | $ 249,900,000 |  |  |  |
Class A Common Stock [Member] | CEO Program [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Maximum number of shares under the controlled equity offering |  |  | 20,000,000 |  |  |  |  |
Common stock, shares issued |  |  |  |  |  |  |  | 20,000,000
Class A Common Stock [Member] | New CEO Program [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Payment percentage of the gross proceeds from the sale of shares | 1.00% |  |  |  |  |  |  |
Common stock, shares issued |  |  |  | 17,600,000 |  |  |  |
Maximum amount under the controlled equity offering program | $ 300,000,000.0 |  |  |  |  |  |  |
Common stock value issued |  |  |  | $ 210,800,000 |  |  |  |

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