Income taxes - Schedule of Future Payments Under Tax Benefit Arrangements (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
2019	$ 24,765
2020	24,996
2021	25,450
2022	25,975
2023	26,482
Thereafter	301,565
Total	$ 429,233	$ 431,360

Income taxes projected future payments under tax benefit arrangements liability.

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Income taxes projected future payments under tax benefit arrangements liability next twelve months.

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Income taxes projected future payments under tax benefit arrangements liability year five.

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Income taxes projected future payments under tax benefit arrangements liability year four.

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Income taxes projected future payments under tax benefit arrangements liability year thereafter.

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Income taxes projected future payments under tax benefit arrangements liability year three.

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Income taxes projected future payments under tax benefit arrangements liability year two.

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