Investments (Activity of OTTI on Investment Securities Due to Credit Losses Recognized in Earnings) (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Disclosure Activity Of O T T I On Investment Securities Due To Credit Losses Recognized In Earnings [Abstract]
Cumulative credit losses on investment securities, through	$ 531,000	$ 531,000
Additions for credit losses not previously recognized	0	0
Cumulative credit losses on investment securities, through	$ 531,000	$ 531,000

This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which no such other than temporary impairment (OTTI) was previously recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563

Name:	us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsNoPreviousImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration