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Schedule II. Condensed Financial Information of Registrant - Condensed Statements of Income (Detail) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Revenues |  |  |  |  |  |  |  |  |  |  |
Net investment income | $ 7,312 | $ 7,788 | $ 7,471 | $ 6,710 | $ 7,855 | $ 8,006 | $ 6,201 | $ 6,044 | $ 29,281 | $ 28,106 | $ 27,902
Fee and other income |  |  |  |  |  |  |  |  | 420 | 347 | 316
Total revenues | 94,937 | 92,804 | 89,925 | 97,542 | 98,558 | 98,206 | 97,563 | 102,335 | 375,208 | 396,662 | 400,954
Expenses |  |  |  |  |  |  |  |  |  |  |
Total expenses |  |  |  |  |  |  |  |  | 292,968 | 283,841 | 299,987
Income tax expense (benefit) |  |  |  |  |  |  |  |  | 36,009 | 34,956 | 30,505
Net income | $ 649 | $ 16,577 | $ 15,481 | $ 13,524 | $ 19,073 | $ 17,896 | $ 16,639 | $ 24,257 | 46,231 | 77,865 | 70,462
Parent Company [Member] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |
Net investment income |  |  |  |  |  |  |  |  | 679 | 1,509 | 854
Fee and other income |  |  |  |  |  |  |  |  | 6,890 | 5,843 | 5,893
Total revenues |  |  |  |  |  |  |  |  | 7,569 | 7,352 | 6,747
Expenses |  |  |  |  |  |  |  |  |  |  |
Other operating costs |  |  |  |  |  |  |  |  | 7,569 | 7,352 | 6,747
Total expenses |  |  |  |  |  |  |  |  | 7,569 | 7,352 | 6,747
Income tax expense (benefit) |  |  |  |  |  |  |  |  | 125 | (156) | (57)
Gain (loss) before equity in earnings of subsidiaries |  |  |  |  |  |  |  |  | (125) | 156 | 57
Equity in net income of subsidiaries |  |  |  |  |  |  |  |  | 46,356 | 77,709 | 70,405
Net income |  |  |  |  |  |  |  |  | $ 46,231 | $ 77,865 | $ 70,462

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