Marketable Securities - Summary of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	$ 27,961
Gross Unrealized Losses	8
Gross Unrealized Gains
U.S. Government and Agency Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	13,557
Gross Unrealized Losses
Gross Unrealized Gains
Corporate Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	8,925
Gross Unrealized Losses	7
Gross Unrealized Gains
FDIC-Insured Certificates of Deposit [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	5,479
Gross Unrealized Losses	1
Gross Unrealized Gains