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Schedule of Restricted Stock Unit Awards Aggregate Intrinsic Value (Detail) - Restricted Stock Units - USD ($) $ / shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Vested	$ 40,649	$ 30,008	$ 32,200
Outstanding	$ 132,875	$ 95,952	$ 84,129
Expected to vest	$ 130,594	$ 91,871	$ 79,611

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested And Expected To Vest Intrinsic Value

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Intrinsic value of equity-based compensation awards outstanding. Excludes stock and unit options.

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Intrinsic value of equity-based compensation awards vested. Excludes stock and unit options.

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