Cash Equivalent and Investments (Parenthetical) (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Minimum [Member] | Fixed Maturity and Mutual Funds [Member]
Schedule Of Investments [Line Items]
Securities Maturity period	14 months	2 months
Minimum [Member] | Short Term Investments [Member]
Schedule Of Investments [Line Items]
Securities Maturity period	14 months	1 month
Maximum [Member] | Certificates Of Deposit [Member]
Schedule Of Investments [Line Items]
Securities Maturity period	90 days
Maximum [Member] | Fixed Maturity and Mutual Funds [Member]
Schedule Of Investments [Line Items]
Securities Maturity period	34 months	23 months
Maximum [Member] | Short Term Investments [Member]
Schedule Of Investments [Line Items]
Securities Maturity period	7 months	10 months