Fair Value Measurements - Additional Information (Detail) (Fair Value, Measurements, Recurring [Member], Level 1 [Member], NAVB Stock [Member])	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | NAVB Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments shares	95,000	95,000