Fair Value Measurements - Schedule of Fair Value Hierarchy of Financial Assets Carried at Fair Value and Measured on Recurring Basis (Detail) - Fair value measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Cash equivalents:
Total cash equivalents		$ 10,139
Debt Securities [Abstract]
Debt securities		7,101
Total assets at fair value	$ 10,799	17,240
LIABILITIES
Acquisition-related contingent consideration liability	2,599	3,421
Total liabilities at fair value	2,599	3,421
U.S. government securities [Member]
Debt Securities [Abstract]
Debt securities		2,000
Commercial paper [Member]
Debt Securities [Abstract]
Debt securities		1,998
Time deposits [Member]
Debt Securities [Abstract]
Debt securities		807
Taxable municipal bonds [Member]
Debt Securities [Abstract]
Debt securities		2,296
U.S. government securities [Member]
Cash equivalents:
Total cash equivalents		2,749
Money market and other funds [Member]
Cash equivalents:
Total cash equivalents	10,799	4,090
Commercial paper [Member]
Cash equivalents:
Total cash equivalents		1,999
Taxable municipal bonds [Member]
Cash equivalents:
Total cash equivalents		1,301
Quoted prices in active markets using identical assets (Level 1) [Member]
Cash equivalents:
Total cash equivalents		0
Debt Securities [Abstract]
Debt securities		0
Total assets at fair value	0
LIABILITIES
Acquisition-related contingent consideration liability	0	0
Total liabilities at fair value	0	0
Quoted prices in active markets using identical assets (Level 1) [Member] | Commercial paper [Member]
Debt Securities [Abstract]
Debt securities		0
Quoted prices in active markets using identical assets (Level 1) [Member] | Time deposits [Member]
Debt Securities [Abstract]
Debt securities		0
Quoted prices in active markets using identical assets (Level 1) [Member] | Taxable municipal bonds [Member]
Debt Securities [Abstract]
Debt securities		0
Quoted prices in active markets using identical assets (Level 1) [Member] | U.S. government securities [Member]
Cash equivalents:
Total cash equivalents		0
Quoted prices in active markets using identical assets (Level 1) [Member] | Money market and other funds [Member]
Cash equivalents:
Total cash equivalents	0	0
Quoted prices in active markets using identical assets (Level 1) [Member] | Commercial paper [Member]
Cash equivalents:
Total cash equivalents		0
Quoted prices in active markets using identical assets (Level 1) [Member] | Taxable municipal bonds [Member]
Cash equivalents:
Total cash equivalents		0
Significant other observable inputs (Level 2) [Member]
Cash equivalents:
Total cash equivalents		10,139
Debt Securities [Abstract]
Debt securities		7,101
Total assets at fair value	10,799	17,240
LIABILITIES
Acquisition-related contingent consideration liability	0	0
Total liabilities at fair value	0	0
Significant other observable inputs (Level 2) [Member] | U.S. government securities [Member]
Debt Securities [Abstract]
Debt securities		2,000
Significant other observable inputs (Level 2) [Member] | Commercial paper [Member]
Debt Securities [Abstract]
Debt securities		1,998
Significant other observable inputs (Level 2) [Member] | Time deposits [Member]
Debt Securities [Abstract]
Debt securities		807
Significant other observable inputs (Level 2) [Member] | Taxable municipal bonds [Member]
Debt Securities [Abstract]
Debt securities		2,296
Significant other observable inputs (Level 2) [Member] | U.S. government securities [Member]
Cash equivalents:
Total cash equivalents		2,749
Significant other observable inputs (Level 2) [Member] | Money market and other funds [Member]
Cash equivalents:
Total cash equivalents	10,799	4,090
Significant other observable inputs (Level 2) [Member] | Commercial paper [Member]
Cash equivalents:
Total cash equivalents		1,999
Significant other observable inputs (Level 2) [Member] | Taxable municipal bonds [Member]
Cash equivalents:
Total cash equivalents		1,301
Significant unobservable inputs (Level 3) [Member]
Cash equivalents:
Total cash equivalents		0
Debt Securities [Abstract]
Debt securities		0
Total assets at fair value	0
LIABILITIES
Acquisition-related contingent consideration liability	2,599	3,421
Total liabilities at fair value	2,599	3,421
Significant unobservable inputs (Level 3) [Member] | Commercial paper [Member]
Debt Securities [Abstract]
Debt securities		0
Significant unobservable inputs (Level 3) [Member] | Time deposits [Member]
Debt Securities [Abstract]
Debt securities		0
Significant unobservable inputs (Level 3) [Member] | Taxable municipal bonds [Member]
Debt Securities [Abstract]
Debt securities		0
Significant unobservable inputs (Level 3) [Member] | U.S. government securities [Member]
Cash equivalents:
Total cash equivalents		0
Significant unobservable inputs (Level 3) [Member] | Money market and other funds [Member]
Cash equivalents:
Total cash equivalents	$ 0	0
Significant unobservable inputs (Level 3) [Member] | Commercial paper [Member]
Cash equivalents:
Total cash equivalents		0
Significant unobservable inputs (Level 3) [Member] | Taxable municipal bonds [Member]
Cash equivalents:
Total cash equivalents		$ 0