Investments and Fair Value Measurements - Summary of Fair Value and Duration of Investments, Including Cash Equivalents, that have been Classified in Gross Unrealized Loss Position (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 63,497	$ 80,664
Gross unrealized gains	200	333
Gross unrealized losses	(147)	(31)
Fair value	63,550	80,966
Less than 12 Months, Fair Value	31,215	30,301
Less than 12 Months, Unrealized Losses	(141)	(27)
More than 12 Months, Fair Value	(233)	(300)
More than 12 Months, Unrealized Losses	(6)	(4)
TOTAL, Fair Value	30,982	30,001
TOTAL, Unrealized Losses	(147)	(31)
U.S. Government and sponsored entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	5,033	17,371
Gross unrealized gains	2	7
Gross unrealized losses	(1)
Fair value	5,034	17,378
Less than 12 Months, Fair Value	1,439	15,791
Less than 12 Months, Unrealized Losses	(1)	(1)
More than 12 Months, Fair Value
More than 12 Months, Unrealized Losses
TOTAL, Fair Value	1,439	15,791
TOTAL, Unrealized Losses	(1)	(1)
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	38,302	40,218
Gross unrealized gains	114	194
Gross unrealized losses	(87)	(17)
Fair value	38,329	40,395
Less than 12 Months, Fair Value	18,228	11,288
Less than 12 Months, Unrealized Losses	(87)	(17)
More than 12 Months, Fair Value
More than 12 Months, Unrealized Losses
TOTAL, Fair Value	18,228	11,288
TOTAL, Unrealized Losses	(87)	(17)
Municipal securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	1,709	1,710
Gross unrealized gains	1	3
Gross unrealized losses	(4)
Fair value	1,706	1,713
Less than 12 Months, Fair Value	831
Less than 12 Months, Unrealized Losses	(4)
More than 12 Months, Fair Value
More than 12 Months, Unrealized Losses
TOTAL, Fair Value	831
TOTAL, Unrealized Losses	(4)
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11,702	12,128
Gross unrealized gains	61	66
Gross unrealized losses	(21)	(2)
Fair value	11,742	12,192
Less than 12 Months, Fair Value	6,935	1,959
Less than 12 Months, Unrealized Losses	(21)	(2)
More than 12 Months, Fair Value
More than 12 Months, Unrealized Losses
TOTAL, Fair Value	6,935	1,959
TOTAL, Unrealized Losses	(21)	(2)
Mortgage-backed securities - residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	6,751	9,237
Gross unrealized gains	22	63
Gross unrealized losses	(34)	(12)
Fair value	6,739	9,288
Less than 12 Months, Fair Value	3,782	1,263
Less than 12 Months, Unrealized Losses	(28)	(7)
More than 12 Months, Fair Value	(233)	(300)
More than 12 Months, Unrealized Losses	(6)	(4)
TOTAL, Fair Value	3,549	963
TOTAL, Unrealized Losses	$ (34)	$ (11)