Borrowings - Convertible Notes - Additional Information (Detail)				1 Months Ended	3 Months Ended			9 Months Ended
	Apr. 18, 2016 shares	Apr. 13, 2016 USD ($) shares	Jul. 31, 2013 USD ($) $ / shares	Jul. 31, 2013 USD ($) $ / shares	Sep. 30, 2016 USD ($) shares	Jun. 30, 2016 USD ($) shares	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) shares	Sep. 30, 2015 USD ($)	Dec. 31, 2015 shares
Debt Instrument [Line Items]
Principal amount of convertible notes due 2020 converted into shares of common stock								$ 64,209,000
Common stock, shares issued | shares					129,435,000			129,435,000		115,871,000
Loss on extinguishment of debt								$ 14,566,000
Transaction costs related to conversion of convertible notes due 2020 in accounts payable, accrued expenses and other								$ 148,000
Debt maturity date								Jul. 15, 2020
Interest expense					$ 6,850,000		$ 4,476,000	$ 36,579,000	$ 13,524,000
Convertible Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount			$ 125,000,000	$ 125,000,000
Net proceeds from the debt issuance				$ 120,600,000
Interest rate (as a percent)			4.50%	4.50%	4.50%			4.50%
Embedded conversion option			$ 53,800,000	$ 53,800,000
Underwriting discounts and commissions and offering expenses			4,400,000
Principal amount of convertible notes due 2020 converted into shares of common stock		$ 64,200,000
Conversion ratio, principal amount		$ 1,000	$ 1,000	$ 1,000
Conversion rate of common stock shares per $1,000 principal amount	136		160
Common stock, shares issued | shares	8,732,152	3,635,511				12,367,663
Value of additional shares issued for conversion		$ 27,700,000
Trading period		10 days
Increase to additional paid in capital pursuant to conversion						$ 101,000,000
Loss on extinguishment of debt						14,600,000
Reduction in additional paid-in capital attributable to embedded conversion option						$ 39,800,000
Number of consecutive trading days during which the closing price of the entity's common stock must exceed the conversion price for at least 20 days in order for the notes to be convertible			30 days
Convertibility of debt, closing price of stock test, percentage of stock price to conversion price for the notes that must be exceeded			130.00%
Number of consecutive business days immediately after any five consecutive trading day period during the note measurement period			5 days
Number of consecutive trading days before five consecutive business days during the note measurement period			5 days
Initial conversion price of shares (in dollars per share) | $ / shares			$ 6.25	$ 6.25
Interest expense					$ 1,700,000		$ 3,400,000	$ 21,100,000	$ 10,300,000
Convertible Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Number of days within 30 consecutive trading days in which the closing price of the entity's common stock must exceed the conversion price for the notes to be convertible			20 days
Convertible Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Convertibility of debt, trading price of debt test, percentage of closing price of stock used in calculation			98.00%
Convertible Notes [Member] | Transaction Costs Incurred With Third Parties [Member]
Debt Instrument [Line Items]
Reduction in additional paid-in capital								200,000
Convertible Notes [Member] | Interest Expense [Member] | Transaction Costs Incurred With Third Parties [Member]
Debt Instrument [Line Items]
Transaction costs related to conversion of convertible notes due 2020 in accounts payable, accrued expenses and other								$ 200,000