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Changes in Accumulated Other Comprehensive (Loss) Income (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Balance | $ 1,480,158 | $ 1,522,354 | $ 1,953,646
Other comprehensive income (loss) | 52,370 | (5,814) | (29,460)
Balance | 2,207,018 | 1,480,158 | 1,522,354
Foreign Currency Translation Reclassification Adjustments |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Balance | (23,514) | (12,523) |
Other comprehensive loss before reclassifications, net of tax | 48,903 | (10,991) |
Amounts reclassified from accumulated other comprehensive income (loss), net of tax | 0 | 0 |
Other comprehensive income (loss) | 48,903 | (10,991) |
Balance | 25,389 | (23,514) | (12,523)
Unrealized Gains (Losses) on Marketable Securities |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Balance | 3,480 | (1,845) |
Other comprehensive loss before reclassifications, net of tax | 5,839 | 6,015 |
Amounts reclassified from accumulated other comprehensive income (loss), net of tax | (2,365) | (690) |
Other comprehensive income (loss) | 3,474 | 5,325 |
Balance | 6,954 | 3,480 | (1,845)
Amortization of Prior Service Credit |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Balance | 1,180 | 1,328 |
Other comprehensive loss before reclassifications, net of tax | 0 | 0 |
Amounts reclassified from accumulated other comprehensive income (loss), net of tax | (7) | (148) | (245)
Other comprehensive income (loss) | (7) | (148) |
Balance | 1,173 | 1,180 | 1,328
Accumulated Other Comprehensive Income (Loss) |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Balance | (18,854) | (13,040) | 18,776
Other comprehensive loss before reclassifications, net of tax | 54,742 | (4,976) |
Amounts reclassified from accumulated other comprehensive income (loss), net of tax | (2,372) | (838) | 1,092
Other comprehensive income (loss) | 52,370 | (5,814) | (29,460)
Balance | $ 33,516 | $ (18,854) | $ (13,040)

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