Stock-Based Compensation (Detail) - Summary Of Changes In CSEs Outstanding - Common stock equivalents (CSEs)	3 Months Ended
	Mar. 31, 2016 $ / shares shares
Common Stock Equivalents (CSEs) [Roll Forward]
Outstanding at December 31, 2014 (in shares) | shares	105,664
Granted (in shares) | shares	1,749
Converted to common shares upon grant (in shares) | shares	(1,400)
Outstanding at September 30, 2015 (in shares) | shares	106,013
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2014 (in Dollars per share) | $ / shares	$ 19.57
Granted (in Dollars per share) | $ / shares	90.58
Converted to common shares upon grant (in Dollars per share) | $ / shares	90.58
Outstanding at September 30, 2015 (in Dollars per share) | $ / shares	$ 19.81