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Parent Company Condensed Financial Information - Statements of Net Income (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Condensed Financial Information [Line Items] |  |  |
Interest expense on long-term debt | $ 790 | $ 617 | $ 746
Net Income | 67,081 | 57,910 | 50,539
Parent Company |  |  |
Condensed Financial Information [Line Items] |  |  |
Dividends from subsidiaries | 75,413 | 46,414 | 24,087
Investment income | 19 | 19 | 15
Interest expense on long-term debt | 773 | 759 | 769
Other expenses | 2,138 | 2,014 | 2,579
Income before Equity in Undistributed Net Income of Subsidiaries | 72,521 | 43,660 | 20,754
Bank subsidiary | (5,064) | 13,351 | 29,926
Nonbank subsidiaries | (376) | 899 | (141)
Net Income | $ 67,081 | $ 57,910 | $ 50,539

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