Borrowings - Convertible Notes - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2013	Jul. 31, 2013	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Debt Instruments [Line Items]
Debt maturity date				Jul. 15, 2020
Interest expense				$ 19,232,000	$ 18,230,000	$ 10,938,000
Convertible Notes [Member]
Schedule Of Debt Instruments [Line Items]
Gross proceeds from the debt issuance		$ 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%
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		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%		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
Conversion ratio, principal amount	$ 1,000	$ 1,000
Conversion rate of common stock shares per $1,000 principal amount	160
Initial conversion price of shares (in dollars per share)	$ 6.25	$ 6.25
Minimum percentage of aggregate principal amount held by bondholders to declare notes due and payable	25.00%
Percentage of principal amount due and payable upon event of default	100.00%
Effective interest rate used to compute initial fair value (as a percent)	15.00%
Fair value of indebtedness	$ 71,200,000	$ 71,200,000
Embedded conversion option	53,800,000	53,800,000
Underwriting discounts and commissions and offering expenses	4,400,000
Debt issuance costs allocated to unamortized debt discount	2,500,000	2,500,000
Debt issuance costs attributable to embedded conversion option	$ 1,900,000	$ 1,900,000
Interest expense				$ 13,700,000	$ 13,700,000	$ 6,200,000
Convertible Notes [Member] | Conversion Terms, Fundamental Changes [Member]
Schedule Of Debt Instruments [Line Items]
Redemption price as percentage of principal amount of notes plus accrued and unpaid interest	100.00%
Convertible Notes [Member] | Conversion Terms, Event of Default [Member]
Schedule Of Debt Instruments [Line Items]
Percentage of principal amount due and payable upon event of default arising out of certain bankruptcy events	100.00%
Convertible Notes [Member] | Minimum [Member]
Schedule Of Debt Instruments [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		20 days
Convertible Notes [Member] | Maximum [Member]
Schedule Of Debt Instruments [Line Items]
Convertibility of debt, trading price of debt test, percentage of closing price of stock used in calculation	98.00%