Fair Value Measurement of Assets and Liabilities - Summary of Company's Financial Instruments, Fair Value on a Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Measurements, Recurring [Member]
Cash equivalents
Total cash equivalents	$ 487	$ 3,476
Available-for-sale:
Total short-term marketable securities	19,178	38,064
Total long-term marketable securities	3,443	1,201
Total financial assets	23,108	42,741
Fair Value, Measurements, Recurring [Member] | Government agency securities [Member]
Available-for-sale:
Total short-term marketable securities	2,351	3,266
Fair Value, Measurements, Recurring [Member] | Municipal bonds [Member]
Available-for-sale:
Total short-term marketable securities	2,829	11,260
Fair Value, Measurements, Recurring [Member] | Certificates of deposit [Member]
Available-for-sale:
Total short-term marketable securities	3,360	6,205
Total long-term marketable securities	1,300	1,201
Fair Value, Measurements, Recurring [Member] | Corporate debentures / bonds [Member]
Available-for-sale:
Total short-term marketable securities	10,638	17,333
Total long-term marketable securities	2,143
Fair Value, Measurements, Recurring [Member] | US Treasury securities [Member]
Cash equivalents
Total cash equivalents	487	3,429
Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Cash equivalents
Total cash equivalents		47
Level 1 [Member]
Cash equivalents
Total cash equivalents	0	47
Available-for-sale:
Total short-term marketable securities	0	0
Total long-term marketable securities	0	0
Total financial assets	0	47
Level 1 [Member] | Government agency securities [Member]
Available-for-sale:
Total short-term marketable securities	0	0
Level 1 [Member] | Municipal bonds [Member]
Available-for-sale:
Total short-term marketable securities	0	0
Level 1 [Member] | Certificates of deposit [Member]
Available-for-sale:
Total short-term marketable securities	0	0
Total long-term marketable securities	0	0
Level 1 [Member] | Corporate debentures / bonds [Member]
Available-for-sale:
Total short-term marketable securities	0	0
Total long-term marketable securities	0
Level 1 [Member] | US Treasury securities [Member]
Cash equivalents
Total cash equivalents	0	0
Level 1 [Member] | Money market funds [Member]
Cash equivalents
Total cash equivalents		47
Level 2 [Member]
Cash equivalents
Total cash equivalents	487	3,429
Available-for-sale:
Total short-term marketable securities	19,178	38,064
Total long-term marketable securities	3,443	1,201
Total financial assets	23,108	42,694
Level 2 [Member] | Government agency securities [Member]
Available-for-sale:
Total short-term marketable securities	2,351	3,266
Level 2 [Member] | Municipal bonds [Member]
Available-for-sale:
Total short-term marketable securities	2,829	11,260
Level 2 [Member] | Certificates of deposit [Member]
Available-for-sale:
Total short-term marketable securities	3,360	6,205
Total long-term marketable securities	1,300	1,201
Level 2 [Member] | Corporate debentures / bonds [Member]
Available-for-sale:
Total short-term marketable securities	10,638	17,333
Total long-term marketable securities	2,143
Level 2 [Member] | US Treasury securities [Member]
Cash equivalents
Total cash equivalents	487	3,429
Level 2 [Member] | Money market funds [Member]
Cash equivalents
Total cash equivalents		$ 0