Activity for Option Plans (Detail) shares in Thousands	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Shares Under Option
Shares Under Options outstanding, beginning balance | shares	768
Shares Under Option, Granted | shares	377
Shares Under Option, Exercised | shares	(304)
Shares Under Option, Forfeited | shares	(6)
Shares Under Options outstanding, ending balance | shares	835
Shares Under Options, Options exercisable, ending balance | shares	203
Weighted-Average Exercise Price
Weighted-Average Exercise Price of Options outstanding, beginning balance | $ / shares	$ 82.45
Weighted-Average Exercise Price, Granted | $ / shares	164.80
Weighted-Average Exercise Price, Exercised | $ / shares	76.25
Weighted-Average Exercise Price, Forfeited | $ / shares	83.58
Weighted-Average Exercise Price of Options outstanding, ending balance | $ / shares	121.89
Weighted-Average Exercise Price, Options exercisable, ending balance | $ / shares	$ 78.30