Investments - Amortized Cost and Gross Unrealized Gains and Losses on All Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 14,896	$ 24,361
FDIC Guaranteed certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	7,100
Common stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,700
Corporate Notes/Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	5,100
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,000
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,259	23,567
Gross Unrealized Gains		806
Gross Unrealized Losses	363	12
Fair Value	14,896	24,361
Short-term Investments [Member] | US Treasury securities and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		3,509
Fair Value		3,509
Short-term Investments [Member] | FDIC Guaranteed certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,120	6,453
Gross Unrealized Losses	6	6
Fair Value	7,114	6,447
Short-term Investments [Member] | Common stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,000	2,000
Gross Unrealized Gains		806
Gross Unrealized Losses	356
Fair Value	1,644	2,806
Short-term Investments [Member] | Corporate Notes/Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,140	4,606
Gross Unrealized Losses	1	4
Fair Value	5,139	4,602
Short-term Investments [Member] | Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	999	6,999
Gross Unrealized Losses		2
Fair Value	$ 999	$ 6,997