Investments (Other-than-temporary Impairment) - Additional Information (Detail)	3 Months Ended	6 Months Ended
Jun. 30, 2015 USD ($) Securities	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Securities	Jun. 30, 2014 USD ($)	Dec. 31, 2014 Securities
Amortized Cost and Fair Value Debt Securities [Abstract]
Number of securities in an unrealized loss position	222		222		94
Number of securities had been in an unrealized loss position for 12 months or greater	7		7		9
Other-than-temporary impairment losses \| $	$ 293,000	$ 0	$ 1,983,000	$ 0

The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 8B

-URI http://asc.fasb.org/extlink&oid=27724398&loc=SL6284393-111563

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