Investments and Fair Value Measurements - Schedule of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity Debt instrument	$ 11,603	$ 11,036
Federal agency [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity Debt instrument	$ 11,603	$ 11,036

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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