Income Taxes - Deferred Income Tax Assets and Liabilities (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2013
Dec. 31, 2012
Deferred income tax assets    
Tax credit carryforwards $ 3,718 $ 0
Stock based compensation 2,049 521
Accrued compensation 5,187 2,109
Deferred revenue 942 1,055
Other 227 114
Total deferred income tax assets 12,123 3,799
Deferred income tax liabilities    
Depreciation and amortization 914 2,125
Prepaid assets 1,484 715
Total deferred income tax liabilities 2,398 2,840
Net deferred income tax assets $ 9,725 $ 959