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Common Stock and Treasury Stock - Additional Information (Detail) - USD ($) | 3 Months Ended | 79 Months Ended |
--- | --- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Mar. 31, 2019 | Feb. 28, 2018
Equity [Abstract] |  |  |  |
Stock authorized to purchase under stock repurchase program |  |  |  | $ 200,000,000
Repurchase of common stock, shares | 23,802 | 1,346,427 | 44,153,195 |
Repurchase of common stock, value | $ 631,000 | $ 31,113,000 | $ 548,500,000 |
Remaining value of shares authorized for purchase under the stock repurchase program | $ 176,000,000 |  | $ 176,000,000 |

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