Summary of Significant Accounting Policies (Tables)
12 Months Ended
Dec. 31, 2013
Accounting Policies [Abstract]  
Activity Related to Provision for Doubtful Accounts
Activity related to our provision for doubtful accounts was as follows:

 
Year Ended December 31,
 
2013
 
2012
 
2011
 
(in thousands)
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