Commitments and Contingencies - Future Minimum Lease Payments Under Leases and Agreements (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Office Leases [Member]
Operating Leased Assets [Line Items]
Remainder of 2013	$ 4,970
2014	7,686
2015	8,655
2016	9,688
2017	9,436
Thereafter	40,087
Total	80,522
Third-Party Hosting Agreements [Member]
Operating Leased Assets [Line Items]
Remainder of 2013	2,902
2014	3,624
2015	3,734
2016	3,844
2017	775
Total	$ 14,879