Cash, Cash Equivalents and Investments - Cash Equivalents and Level 1 Investments Measured at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	$ 38,138	$ 38,102
Money market funds and other cash equivalents [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	4,981	4,500
Certificates of deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,393	5,062
U.S. government agency bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	8,291	8,498
Municipal bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	11,450	10,162
Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	11,023	9,880
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	7,374	9,562
Level 1 [Member] | Money market funds and other cash equivalents [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	4,981	4,500
Level 1 [Member] | Certificates of deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,393	5,062
Level 1 [Member] | U.S. government agency bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Level 1 [Member] | Municipal bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Level 1 [Member] | Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	30,764	28,540
Level 2 [Member] | Money market funds and other cash equivalents [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	0	0
Level 2 [Member] | Certificates of deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Level 2 [Member] | U.S. government agency bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	8,291	8,498
Level 2 [Member] | Municipal bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	11,450	10,162
Level 2 [Member] | Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	11,023	9,880
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	0	0
Level 3 [Member] | Money market funds and other cash equivalents [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	0	0
Level 3 [Member] | Certificates of deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Level 3 [Member] | U.S. government agency bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Level 3 [Member] | Municipal bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Level 3 [Member] | Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 0	$ 0