Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Significant Accounting Policies [Line Items]
Maximum maturity period for classification of investments as cash equivalents	3 months
Investments other-than-temporary losses	$ 0	$ 0	$ 0
Contractual maturities accounts receivable	less than one year
Allowance for doubtful accounts	$ 109,000	3,000	100,000
Provision for bad debts	200,000	100,000	200,000
Write-offs and other charges against the allowance for doubtful accounts	$ 100,000	0	100,000
Term for post-contract technical support	1 year
Term of agreement for revenue recognition	2 years
Employee compensation and benefits	$ 83,856,000	74,995,000	64,406,000
Depreciation and amortization	18,542,000	17,379,000	$ 14,123,000
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	30,897,000	$ 32,185,000
Restatement Adjustment [Member]
Significant Accounting Policies [Line Items]
Employee compensation and benefits	2,900,000
Depreciation and amortization	1,300,000
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	$ 1,600,000
Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of fixed assets	3 years
Minimum [Member] | Business Combinations [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	3 years
Minimum [Member] | Internally Developed Software [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of fixed assets	7 years
Maximum [Member] | Business Combinations [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	15 years