Preferred Stock - Number of Shares Issued and Outstanding and Carrying Amount of Preferred Stock (Parenthetical) (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Preferred stock, par value	$ 1.00	$ 1.00

Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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)

-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

-Article 5

Name:	us-gaap_PreferredStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant