Investments - Investments in Continuous Unrealized Loss Position for Twelve Months or More (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 100,071	$ 36,271
Unrealized Losses	(268)	(30)
Corporate bonds and notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	100,071	34,772
Unrealized Losses	(268)	(29)
Municipal bonds and notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value		1,499
Unrealized Losses		$ (1)