Investments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013 Bonds	Dec. 31, 2012	Dec. 31, 2011
Net Investment Income [Line Items]
Certificates of deposit with an amortized cost	$ 7,246,000
Money market funds with a cost and fair value	6,986,000	3,771,000
Investment grade corporate bond	108
Weighted average yield-to-book value of investment grade corporate bonds	2.94%
Weighted average maturity of investment grade corporate bonds	5 years 8 months 5 days
Realized gain	0	40,000
Other than temporary impairment charges	0	0	0
Investments in a material unrealized loss position for greater than one year	0	0
A - or Better [Member]
Net Investment Income [Line Items]
Number of security investment held by entity	89
BBB- to BBB+ [Member]
Net Investment Income [Line Items]
Number of security investment held by entity	19
Certificates of deposit, short term [Member]
Net Investment Income [Line Items]
Certificates of deposit with an amortized cost	1,250,000	1,200,000
Money market funds [Member]
Net Investment Income [Line Items]
Certificates of deposit with an amortized cost	60,000
Money market funds with a cost and fair value	60,000	93,000
Investment grade corporate bonds [Member]
Net Investment Income [Line Items]
Certificates of deposit with an amortized cost	$ 5,936,000	$ 2,871,000