Investments - Amortized Cost and Gross Unrealized Gains and Losses on All Securities (Detail) (Short-term Investments [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 17,953	$ 23,567
Gross Unrealized Gains		806
Gross Unrealized Losses	13	12
Fair Value	17,940	24,361
US Treasury securities and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,503	3,509
Fair Value	1,503	3,509
FDIC Guaranteed certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,333	6,453
Gross Unrealized Losses	8	6
Fair Value	8,325	6,447
Common stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,000	2,000
Gross Unrealized Gains		806
Fair Value	2,000	2,806
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,119	4,606
Gross Unrealized Losses	5	4
Fair Value	5,114	4,602
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	998	6,999
Gross Unrealized Losses		2
Fair Value	$ 998	$ 6,997