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Dividends Declared Per Share (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Dividends Payable [Line Items]
Dividend Amount	$ 0.355	$ 0.350	$ 1.065	$ 1.050
Group One
Dividends Payable [Line Items]
Declaration Date			Oct. 19, 2016
Date Paid (Payable)			Nov. 28, 2016
Shareholder of Record Date			Nov. 14, 2016
Dividend Amount			$ 0.355
Group Two
Dividends Payable [Line Items]
Declaration Date			Jul. 20, 2016
Date Paid (Payable)			Aug. 26, 2016
Shareholder of Record Date			Aug. 12, 2016
Dividend Amount			$ 0.355
Group Three
Dividends Payable [Line Items]
Declaration Date			Apr. 20, 2016
Date Paid (Payable)			May 27, 2016
Shareholder of Record Date			May 13, 2016
Dividend Amount			$ 0.355
Group Four
Dividends Payable [Line Items]
Declaration Date			Jan. 27, 2016
Date Paid (Payable)			Feb. 26, 2016
Shareholder of Record Date			Feb. 12, 2016
Dividend Amount			$ 0.355
Group Five
Dividends Payable [Line Items]
Declaration Date			Oct. 21, 2015
Date Paid (Payable)			Nov. 27, 2015
Shareholder of Record Date			Nov. 13, 2015
Dividend Amount			$ 0.350
Group Six
Dividends Payable [Line Items]
Declaration Date			Jul. 22, 2015
Date Paid (Payable)			Aug. 28, 2015
Shareholder of Record Date			Aug. 14, 2015
Dividend Amount			$ 0.350
Group Seven
Dividends Payable [Line Items]
Declaration Date			Apr. 22, 2015
Date Paid (Payable)			May 28, 2015
Shareholder of Record Date			May 14, 2015
Dividend Amount			$ 0.350
Group Eight
Dividends Payable [Line Items]
Declaration Date			Jan. 26, 2015
Date Paid (Payable)			Feb. 27, 2015
Shareholder of Record Date			Feb. 13, 2015
Dividend Amount			$ 0.350

X

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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- Definition

Date the declared dividend will be paid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

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- Definition

Date the dividend to be paid was declared, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

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- Definition

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

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