Nature of Business and Summary of Significant Accounting Policies - Number of Shares Outstanding for Calculation of Earnings (Loss) Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Basic net income and earnings per share, Numerator (Income)	$ 2,767	$ (1,461)	$ 3,043	$ 2,208	$ 1,860	$ 3,703	$ 4,493	$ 3,021	$ 13,077	$ 6,557	$ 10,850
Common stock equivalents arising from stock options and employee stock purchase plan, Numerator (Income)									0	0	0
Subordinated convertible promissory notes, Numerator (Income)											303
Diluted net income and earnings per share, Numerator (Income)									$ 13,077	$ 6,557	$ 11,153
Basic net income and earnings per share, Denominator (Shares)									25,750,972	20,116,991	14,813,186
Common stock equivalents arising from stock options and employee stock purchase plan, Denominator (Shares)									446,000	603,000	327,000
Subordinated convertible promissory notes, Denominator (shares)											2,106,000
Diluted net income and earnings per share, Denominator (Shares)									26,196,901	20,719,951	17,246,058
Basic net income and earnings per share, Per Share Amount	$ 0.11	$ (0.07)	$ 0.17	$ 0.13	$ 0.07	$ 0.14	$ 0.18	$ 0.12	$ 0.51	$ 0.33	$ 0.73
Common stock equivalents arising from stock options and employee stock purchase plan, Per share amount									$ (0.01)	$ (0.01)
Subordinated convertible promissory notes, Per Share Amount											$ (0.08)
Diluted net income and earnings per share	$ 0.11	$ (0.07)	$ 0.17	$ 0.12	$ 0.07	$ 0.14	$ 0.17	$ 0.12	$ 0.50	$ 0.32	$ 0.65