Fair Values of Financial Instruments - Available-for-Sale Securities Measured at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 5,437	$ 13,511
Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	2,189	2,173
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	3,248	3,699
Asset-backed securities and collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities		7,639
Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities
Level 1 [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities
Level 1 [Member] | Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities
Level 1 [Member] | Asset-backed securities and collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities
Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	5,437	7,954
Level 2 [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	2,189	2,173
Level 2 [Member] | Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	3,248	3,699
Level 2 [Member] | Asset-backed securities and collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities		2,082
Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities		5,557
Level 3 [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities
Level 3 [Member] | Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities
Level 3 [Member] | Asset-backed securities and collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities		$ 5,557