Fair Value of Financial Instruments - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2013 Level 1 [Member]	Dec. 31, 2013 Level 3 [Member]	Dec. 31, 2013 Corporate Debt Securities [Member]	Dec. 31, 2013 Corporate Debt Securities [Member] Level 2 [Member]	Dec. 31, 2013 Corporate Debt Securities [Member] Level 3 [Member]	Dec. 31, 2013 Commercial Paper [Member]	Dec. 31, 2013 Commercial Paper [Member] Level 2 [Member]	Dec. 31, 2013 Commercial Paper [Member] Level 3 [Member]	Dec. 31, 2012 Recurring Basis [Member] Level 1 [Member]	Dec. 31, 2012 Recurring Basis [Member] Level 2 [Member]	Dec. 31, 2012 Recurring Basis [Member] Level 3 [Member]	Dec. 31, 2012 Recurring Basis [Member] Certificates of Deposit [Member] Level 1 [Member]	Dec. 31, 2012 Recurring Basis [Member] Certificates of Deposit [Member] Level 2 [Member]	Dec. 31, 2012 Recurring Basis [Member] Certificates of Deposit [Member] Level 3 [Member]	Dec. 31, 2012 Recurring Basis [Member] Corporate Debt Securities [Member] Level 1 [Member]	Dec. 31, 2012 Recurring Basis [Member] Corporate Debt Securities [Member] Level 2 [Member]	Dec. 31, 2012 Recurring Basis [Member] Corporate Debt Securities [Member] Level 3 [Member]	Dec. 31, 2012 Recurring Basis [Member] Commercial Paper [Member] Level 1 [Member]	Dec. 31, 2012 Recurring Basis [Member] Commercial Paper [Member] Level 2 [Member]
Assets:
Cash equivalents - money market funds		$ 47,740								$ 25,668
Cash equivalents								13,998						480			5,017
Investments	90,116			40,436	40,436		49,680	49,680						240			59,533			12,465
Liabilities:
Derivative liability												$ 196