Cash Equivalent and Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Minimum | fixed maturity and open ended mutual funds [Member]
Schedule Of Investments [Line Items]
securities, maturity period	6 months
Minimum | short term investment
Schedule Of Investments [Line Items]
securities, maturity period	1 month	1 month
Maximum | certificate of deposit
Schedule Of Investments [Line Items]
securities, maturity period	90 days
Maximum | fixed maturity and open ended mutual funds [Member]
Schedule Of Investments [Line Items]
securities, maturity period	23 months
Maximum | short term investment
Schedule Of Investments [Line Items]
securities, maturity period	10 months	9 months