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Capital Management - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Oct. 31, 2015
Equity [Abstract]
Share repurchase new limit amount							$ 25.0
Share repurchase program expiration date				Dec. 31, 2016
Shares repurchased	1,258,250	1,258,250		1,258,250	1,258,250
Shares repurchased, value	$ 22.4			$ 22.4
Shares repurchased, average price				$ 17.78
Quarterly dividend	$ 0.15	$ 0.12		0.15	$ 0.12	$ 0.08
Extraordinary cash dividends declared per common share	$ 3.00	$ 1.00	$ 0.50	$ 3.00	$ 1.50	$ 0.00

X

- Definition

Share Purchased Under Share Repurchase Program Value.

+ References

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X

- Definition

Share Repurchases Price Paid Per Share.

+ References

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X

- Definition

Special cash dividend declared per share.

+ References

No definition available.

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X

- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ 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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X

- References

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X

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

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X

- Definition

Expiration date for the purchase of an entity's own shares under a stock repurchase plan, in the CCYY-MM-DD format.

+ References

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X

- Definition

Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.28,29)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30
-Article 5

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