Common Stock, Preferred Stock and Stockholders' Deficit (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended		0 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jul. 02, 2013 IPO - conversion of mandatorily redeemable convertible preferred stock, Series F Pro Forma	Jul. 02, 2013 Common stock IPO - conversion of mandatorily redeemable convertible preferred stock, Series F	Jun. 30, 2013 Series A	Dec. 31, 2012 Series A	Jun. 30, 2013 Series B	Dec. 31, 2012 Series B	Jun. 30, 2013 Series B-1	Dec. 31, 2012 Series B-1	Jun. 30, 2013 Series C	Dec. 31, 2012 Series C	Jun. 30, 2013 Series D	Dec. 31, 2012 Series D	Jun. 30, 2013 Series E	Dec. 31, 2012 Series E	Jun. 30, 2013 Series 1	Dec. 31, 2012 Series 1	Jun. 30, 2013 Series 2	Dec. 31, 2012 Series 2	Jun. 30, 2013 Series 3	Dec. 31, 2012 Series 3	Jun. 30, 2013 Series 4	Dec. 31, 2012 Series 4	Jun. 30, 2013 Series F	Dec. 31, 2012 Series F	Jun. 30, 2013 Preferred stock excluding Series B-1
Mandatorily Redeemable Convertible Preferred Stock
Mandatorily redeemable convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Authorized (in shares)	32,742,929	32,742,929			6,861,975	6,861,975	3,500,732	3,500,732	548,032	548,032	5,308,216	5,308,216	5,453,975	5,453,975	238,000	238,000	979,333	979,333	1,822,000	1,822,000	937,333	937,333	3,093,333	3,093,333	4,000,000	4,000,000
Issued (in shares)	32,563,192	32,563,192			6,826,451	6,826,451	3,500,729	3,500,729	514,102	514,102	5,276,554	5,276,554	5,453,970	5,453,970	236,108	236,108	947,711	947,711	1,821,455	1,821,455	928,054	928,054	3,092,932	3,092,932	3,965,126	3,965,126
Outstanding (in shares)	32,563,192	32,563,192			6,826,451	6,826,451	3,500,729	3,500,729	514,102	514,102	5,276,554	5,276,554	5,453,970	5,453,970	236,108	236,108	947,711	947,711	1,821,455	1,821,455	928,054	928,054	3,092,932	3,092,932	3,965,126	3,965,126
Original Issue Price (in dollars per share)					$ 1.2669	$ 1.2669	$ 3.1422	$ 3.1422	$ 4.8629	$ 4.8629	$ 3.7904	$ 3.7904	$ 7.3341	$ 7.3341	$ 8.0051	$ 8.0051	$ 2.4575	$ 2.4575	$ 4.1387	$ 4.1387	$ 5.7507	$ 5.7507	$ 2.7548	$ 2.7548	$ 9.3314	$ 9.3314
Liquidation Preference					$ 8,648	$ 8,648	$ 11,000	$ 11,000	$ 2,500	$ 2,500	$ 20,000	$ 20,000	$ 40,000	$ 40,000	$ 1,890	$ 1,890	$ 2,329	$ 2,329	$ 7,538	$ 7,538	$ 5,337	$ 5,337	$ 8,520	$ 8,520	$ 37,000	$ 37,000
Carrying Value	162,657	162,466			8,435	8,402	10,956	10,949	2,482	2,479	19,941	19,932	39,940	39,931	1,890	1,890	5,217	5,217	12,404	12,404	7,517	7,517	17,722	17,722	36,153	36,023
Dividend Rate (in dollars per share)					$ 0.10140		$ 0.25140		$ 0.38910		$ 0.30330		$ 0.58680		$ 0.64035		$ 0.19665		$ 0.33105		$ 0.46005		$ 0.22035		$ 0.74655
Common stock dividends declared or paid	0
Conversion Rate									1.04719																		1
Maximum initial public offering price for ratchet provision (in dollars per share)																									$ 13.997
IPO price (in dollars per share)				$ 10.00
Common stock issued on automatic conversion of preferred stock (in shares)				5,549,989
Shares of common stock issued on conversion related to the ratchet provision				1,584,863
Expenses related to the issuance of additional shares for the ratchet provision			$ 15,849