Changes in the Shares of Common Stock Outstanding (Detail)	6 Months Ended
	Jun. 30, 2017 shares
Stockholders Equity Note [Abstract]
Beginning balance	29,386,882
Restricted common stock awards granted, net of forfeitures	391,668
Restricted stock units converted to common stock	21,387
Common stock options exercised	750
Common stock acquired	(5,909)
Ending balance	29,794,778