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Common Stock Repurchase Programs - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Aug. 31, 2018
Common Stock [Line Items]
Common stock authorized for repurchase				$ 500,000
Common stock repurchased		$ 78,982	$ 250,000
Subsequent Event [Member]
Common Stock [Line Items]
Stock repurchased and retired during period, shares	817,950
Stock repurchased and retired during period, value	$ 21,400
Common Stock [Member]
Common Stock [Line Items]
Common stock repurchased		$ 25
Repurchased common stock, shares		2,525,000
Restricted Stock [Member]
Common Stock [Line Items]
Number of shares withheld to satisfy minimum statutory tax withholding obligations		19,331
Amount withheld to satisfy minimum statutory tax withholding obligations		$ 600

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Common Stock [Line Items]

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For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

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Amount of stock repurchase plan authorized.

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Number of shares that have been repurchased and retired during the period.

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Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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