Aggregate dividends declared during the period for each share of common stock outstanding.

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Face amount or stated value per share of common stock.

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Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

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Describes the declaration as being a special dividend (over and above the normal dividend); as the annual, semi-annual, quarterly dividend, or other normal periodic dividend; or as some other type of dividend.

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Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

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Amount of stock repurchase plan authorized.

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Amount remaining of a stock repurchase plan authorized.

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Stockholders Equity Note [Line Items]

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Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	6 Months Ended
	Mar. 15, 2018	Feb. 28, 2018	Jun. 30, 2018	Nov. 30, 2015
Stockholders Equity Note [Line Items]
Par value of common stock			$ 1.00
Dividends paid	$ 154,000		$ 153,967
Dividend Declared [Member]
Stockholders Equity Note [Line Items]
Dividend record date		Mar. 05, 2018
Special dividend per share		$ 10
Dividend payable nature		Special
2015 Repurchase Program
Stockholders Equity Note [Line Items]
Aggregate amount of common stock authorized for repurchase				$ 400,000
2018 Repurchase Program
Stockholders Equity Note [Line Items]
Aggregate amount of common stock authorized for repurchase			400,000
2015 Repurchase Program and 2018 Repurchase Program
Stockholders Equity Note [Line Items]
Remaining authorized repurchases under share repurchase program			$ 527,100