Borrowings - 2022 Notes - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Dec. 22, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule Of Debt Instruments [Line Items]
Loss on extinguishment of debt				$ 4,887	$ 14,566
Interest expense		$ 1,659	$ 1,560	30,400	20,708
2022 Notes [Member]
Schedule Of Debt Instruments [Line Items]
Aggregate principal amount	$ 175,000
Net proceeds from the debt issuance	$ 168,500
Interest rate (as a percent)	11.50%
Loss on extinguishment of debt				25,000
Prepayment penalty of extinguishment of debt				20,100
Amortization expense recognized for remaining debt discount at settlement				4,900
Interest expense		$ 0	$ 5,200	6,700	$ 15,600
2022 Notes [Member] | Interest Expense [Member]
Schedule Of Debt Instruments [Line Items]
Loss on extinguishment of debt				$ 25,000