Stock-Based Compensation Expense - Summary of Restricted Stock and Restricted Stock Unit Activity (Detail)	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Restricted Stock [Member]
Shares
Unvested balance, Beginning balance (in shares) | shares	585,004
Granted (in shares) | shares	0
Vested (in shares) | shares	(156,765)
Forfeited (in shares) | shares	(7,698)
Unvested balance, Ending balance (in shares) | shares	420,541
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 18.05
Granted (in dollars per share) | $ / shares	0.00
Vested (in dollars per share) | $ / shares	19.04
Forfeited (in dollars per share) | $ / shares	23.01
Ending Balance (in dollars per share) | $ / shares	$ 17.59
Restricted Stock Units (RSUs) [Member]
Shares
Unvested balance, Beginning balance (in shares) | shares	734,577
Granted (in shares) | shares	1,423,010
Vested (in shares) | shares	(200,416)
Forfeited (in shares) | shares	(78,441)
Unvested balance, Ending balance (in shares) | shares	1,878,730
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 13.47
Granted (in dollars per share) | $ / shares	14.11
Vested (in dollars per share) | $ / shares	13.72
Forfeited (in dollars per share) | $ / shares	13.62
Ending Balance (in dollars per share) | $ / shares	$ 13.92