Quarterly Information (Unaudited) - Statement of Operations Data (Detail) (USD $)
In Thousands, except Per Share data, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]                      
Revenue $ 45,181 $ 42,970 $ 40,670 $ 37,437 $ 36,985 $ 35,368 $ 33,797 $ 32,688 $ 166,258 $ 138,837 $ 119,461
Gross profit 40,235 38,285 35,894 33,028 33,010 31,681 30,372 29,271 147,442 124,333 108,887
Income (loss) from operations 2,636 2,191 (123) (6,630) 1,034 1,549 2,256 1,172 (1,926) 6,011 9,498
Net income (loss) $ (459) $ (56) $ (1,360) $ (5,807) $ 2,196 $ 718 $ 576 $ 76 $ (7,682) $ 3,566 $ 5,761
Net income (loss) per share-basic $ (0.02) $ 0.00 $ (0.06) $ (0.24) $ 0.14 $ 0.03 $ 0.02 $ 0.00 $ (0.32) $ 0.14 $ 0.24
Net income (loss) per share-diluted $ (0.02) $ 0.00 $ (0.06) $ (0.24) $ 0.14 $ 0.03 $ 0.02 $ 0.00 $ (0.32) $ 0.14 $ 0.23