Stockholders' Equity (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Summary of stock-based compensation expense
Total stock-based compensation	$ 5,653	$ 2,968	$ 15,260	$ 8,104
Cost of revenue [Member]
Summary of stock-based compensation expense
Total stock-based compensation	763	470	2,050	1,286
Sales and marketing [Member]
Summary of stock-based compensation expense
Total stock-based compensation	2,180	1,111	5,836	2,981
Research and development [Member]
Summary of stock-based compensation expense
Total stock-based compensation	562	327	1,455	864
General and administrative [Member]
Summary of stock-based compensation expense
Total stock-based compensation	$ 2,148	$ 1,060	$ 5,919	$ 2,973