Summary of Significant Accounting Policies - Summary of Reconciliation of Amounts in Previously Reported Consolidated Financial Statements - Statement of Stockholders' Equity (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Quantifying Misstatement In Current Year Financial Statements [Line Items]
Accumulated deficit	$ (1,366,329)	$ (1,404,670)
Total stockholders' equity	$ 597,305	556,607
As Reported [Member]
Quantifying Misstatement In Current Year Financial Statements [Line Items]
Accumulated deficit		(1,414,561)
Total stockholders' equity		546,716
Adjustment [Member]
Quantifying Misstatement In Current Year Financial Statements [Line Items]
Accumulated deficit		9,891
Total stockholders' equity		$ 9,891