Equity Compensation Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Stockholders Equity [Line Items]
Share based awards, authorized	27,200,000
Options outstanding	8,856,208	10,322,903
Common Stock
Stockholders Equity [Line Items]
Vesting period, years	3 years
Board of Directors Chairman
Stockholders Equity [Line Items]
Outstanding options expiration term, years	10 years
Options to purchase shares of common stock, percentage	100.00%
Independent Director | Common Stock
Stockholders Equity [Line Items]
Initial equity grant value	$ 550,000
Average closing price of common stock, trailing period	3 months
Additional equity grant value	$ 375,000
Stock Option | Board of Directors Chairman
Stockholders Equity [Line Items]
Options to purchase shares of common stock, percentage	50.00%
Stock Option | Independent Director
Stockholders Equity [Line Items]
Options to purchase shares of common stock, percentage	60.00%
Employee Stock Purchase Plan
Stockholders Equity [Line Items]
Share based awards, authorized	3,500,000
Shares reserved for future issuance	800,000
Percentage of fair market value of the stock purchased	85.00%
Span of offering period, in years	2 years
Maximum percentage of qualified compensation to be used for purchase	10.00%
Maximum payroll deductions	$ 25,000
Shares issued under the Employee Stock Purchase Plan	200,000
Unvested restricted stock units
Stockholders Equity [Line Items]
Vesting period, years	1 year
Unvested restricted stock units | Common Stock
Stockholders Equity [Line Items]
Vesting period, years	1 year
Unvested restricted stock units | Board of Directors Chairman
Stockholders Equity [Line Items]
Options to purchase shares of common stock, percentage	50.00%
Unvested restricted stock units | Independent Director
Stockholders Equity [Line Items]
Vesting period, years	3 years
Options to purchase shares of common stock, percentage	40.00%
Share Incentive Plan
Stockholders Equity [Line Items]
Share based awards, authorized	41,500,000
Shares reserved for future issuance	24,300,000
Options outstanding	8,900,000
Share Incentive Plan | Stock Option
Stockholders Equity [Line Items]
Vesting period, years	4 years
Initial time period vesting requirements, months	6 months
Outstanding options expiration term, years	10 years
Share Incentive Plan | Restricted Stock With Service Based Vesting Conditions
Stockholders Equity [Line Items]
Vesting period, years	4 years
Share Incentive Plan | Restricted Stock With Service Based Vesting Conditions | Board of Directors Chairman
Stockholders Equity [Line Items]
Vesting period, years	1 year