Cash Value of Life Insurance - Summary of Activity in Balance of Cash Value of Life Insurance (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 30, 2014 Policies Company Employees	Sep. 30, 2013 Company Employees Policies
Increase (Decrease) in Insurance Liabilities [Abstract]
Beginning balance	$ 52,309	$ 50,582
Increase in cash value of life insurance	1,287	1,337
Ending balance	53,596	51,919
End of period death benefit	$ 95,896	$ 95,206
Number of policies owned	133	133
Insurance companies used	6	6
Current and former employees and directors covered	36	36

Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity.

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 210.5-02.17)

-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 17

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 4

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6812-107765

Name:	us-gaap_CashSurrenderValueOfLifeInsurance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant