Stock-Based Compensation and Stock Awards - Summary of RSA Activity (Detail) - Restricted Stock Awards	12 Months Ended
	Dec. 31, 2017 $ / shares shares
RSA Number of Shares
Nonvested options, Beginning Balance (in shares) | shares	269,383
Granted (in shares) | shares	261,095
Vested (in shares) | shares	(127,674)
Forfeited (in shares) | shares	(5,506)
Nonvested options, Ending Balance (in shares) | shares	397,298
Weighted Average Grant Date Fair Value Per Unit
Nonvested Weighted Average Grant Date Fair Value, Beginning Balance (in dollars per share) | $ / shares	$ 57.59
Granted (in dollars per share) | $ / shares	43.56
Vested (in dollars per share) | $ / shares	55.31
Forfeited (in dollars per share) | $ / shares	52.81
Nonvested Weighted Average Grant Date Fair Value, Ending Balance (in dollars per share) | $ / shares	$ 46.76