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.

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

Name:	us-gaap_TreasuryStockShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Treasury Stock - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended			3 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2011	Mar. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Share repurchase new limit amount	$ 25.0	$ 25.0	$ 25.0
Share repurchase program expiration date				Dec. 31, 2014
Shares repurchased				1,258,250	1,258,250
Shares repurchased, value				$ 22.4
Shares repurchased, average price				$ 17.78