Summary of Significant Accounting Policies Activity Related to Allowance for Doubtful Accounts (Details) (Allowance for doubtful accounts, USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Allowance for doubtful accounts
     
Valuation Allowance [Line Items]      
Balance at the beginning of the period $ 307 $ 135 $ 21
Bad debt expense 789 321 133
Accounts written off (291) (149) (19)
Balance at the end of the period $ 805 $ 307 $ 135