Total Revenue by Geography (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Segment Reporting Information [Line Items]
Total revenue	$ 98,077	$ 91,567	$ 84,545	$ 76,361	$ 89,462	$ 83,297	$ 72,624	$ 63,296	$ 350,550	$ 308,679	$ 290,540
United States
Segment Reporting Information [Line Items]
Total revenue									262,020	230,359	211,711
Europe
Segment Reporting Information [Line Items]
Total revenue									42,884	32,998	37,921
Asia
Segment Reporting Information [Line Items]
Total revenue									18,107	17,637	16,260
Rest of the world
Segment Reporting Information [Line Items]
Total revenue									$ 27,539	$ 27,685	$ 24,648