Stockholders' Equity - Warrants Issued for Services (Details) (USD $)	6 Months Ended		0 Months Ended	1 Months Ended			0 Months Ended	3 Months Ended		6 Months Ended			1 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended		6 Months Ended		1 Months Ended				0 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Aug. 29, 2013 Common Stock Purchase Warrants Revolving line of credit	Jun. 30, 2014 Common Stock Purchase Warrants Revolving line of credit	Aug. 29, 2013 Common Stock Purchase Warrants Revolving line of credit	Jun. 13, 2013 Common Stock Purchase Warrants Revolving line of credit	Feb. 25, 2011 Common Stock Purchase Warrants Third Party Marketing Firm	Jun. 30, 2014 Common Stock Purchase Warrants Third Party Marketing Firm	Jun. 30, 2013 Common Stock Purchase Warrants Third Party Marketing Firm	Jun. 30, 2014 Common Stock Purchase Warrants Third Party Marketing Firm	Jun. 30, 2013 Common Stock Purchase Warrants Third Party Marketing Firm	Feb. 25, 2011 Common Stock Purchase Warrants Third Party Marketing Firm	May 31, 2014 Common Stock Purchase Warrants Service Provider	Jun. 30, 2014 Common Stock Purchase Warrants Service Provider	Jun. 30, 2014 Common Stock Purchase Warrants Service Provider	May 31, 2014 Common Stock Purchase Warrants USAA	Jun. 30, 2014 Common Stock Purchase Warrants USAA	Jun. 30, 2013 Common Stock Purchase Warrants USAA	Jun. 30, 2014 Common Stock Purchase Warrants USAA	Jun. 30, 2013 Common Stock Purchase Warrants USAA	May 31, 2014 Common Stock Purchase Warrants USAA Affinity Group Marketing Agreement tranche	May 31, 2014 Tranche One Common Stock Purchase Warrants USAA Affinity Group Marketing Agreement	May 31, 2014 Tranche Two Common Stock Purchase Warrants USAA Affinity Group Marketing Agreement	Jun. 13, 2012 Draws on credit facility at any time after issuance date Common Stock Purchase Warrants Revolving line of credit	Jun. 13, 2012 Advances greater than $4.0 million at any time after issuance date Common Stock Purchase Warrants Revolving line of credit	Jun. 13, 2012 Advances greater than $4.0 million at any time after issuance date Common Stock Purchase Warrants Revolving line of credit
Warrants Issued for Services
Shares that may be purchased under warrant				66,666	66,666								333,333								1,458,979	392,313	1,066,666	26,666		66,666
Exercise price of warrants (in dollars per share)					$ 7.92	$ 7.92						$ 6.02	$ 12.81									$ 7.95	$ 15.00	$ 11.51
Number of warrant tranches																					2
Maximum number of shares under warrant agreement							1,433,333									3,265,168
Exercise of warrants	$ 9,461,000															$ 9,500,000
Warrant expense	4,668,000	1,262,000						400,000	500,000	2,300,000	700,000			400,000	400,000		1,600,000	300,000	1,900,000	400,000
Number of shares under warrants that have been earned								104,992	134,400	343,665	268,800				33,333		201,056	120,495	340,558	154,294
Warrant vesting period													4 years
Period of warrant							8 years						5 years
Shares issued for exercise of warrants				27,526
Threshold borrowings under the credit facility for higher number of shares under warrant																									4,000,000
Amount drawn on credit facility			$ 5,000,000
Period of warrant from termination date of agreement													12 months