Cash, Equivalents and Marketable Securities - Summary of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	$ 121,103	$ 139,698
Cash and cash equivalents, Marketable securities, Amortized Cost	126,162	144,755
Cash and cash equivalents, Gross Unrealized Gains
Cash and cash equivalents, Marketable securities, Gross Unrealized Gains	1,702	733
Cash and cash equivalents, Gross Unrealized Losses
Cash and cash equivalents, Marketable securities, Gross Unrealized Losses
Cash and cash equivalents, Estimate fair Value	121,103	139,698
Cash and cash equivalents, Marketable securities, Estimated fair Value	127,864	145,488
Cash and cash equivalents	121,103	139,698
Marketable Security, Current	3,312	3,310
Marketable Security, Long Term	3,449	2,480
Bank CDs [Member]
Schedule of Investments [Line Items]
Marketable security, Amortized Cost	252	987
Marketable security, Gross Unrealized Gains
Marketable security, Gross Unrealized Losses
Marketable security, Estimated fair Value	252	987
Cash and cash equivalents
Marketable Security, Current	252	987
Marketable Security, Long Term
Money market currency funds [Member]
Schedule of Investments [Line Items]
Marketable security, Amortized Cost	3,060	2,323
Marketable security, Gross Unrealized Gains
Marketable security, Gross Unrealized Losses
Marketable security, Estimated fair Value	3,060	2,323
Cash and cash equivalents
Marketable Security, Current	3,060	2,323
Marketable Security, Long Term
Other securities (included in other assets) [Member]
Schedule of Investments [Line Items]
Marketable security, Amortized Cost	1,747	1,747
Marketable security, Gross Unrealized Gains	1,702	733
Marketable security, Gross Unrealized Losses
Marketable security, Estimated fair Value	3,449	2,480
Cash and cash equivalents
Marketable Security, Current
Marketable Security, Long Term	$ 3,449	$ 2,480