Share-based Compensation Plans - Schedule of Stock Options Outstanding and Exercisable by Exercise Price Range (Detail)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
$10.42 - $21.78 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	$ 10.42
Exercise price, high end of range (in dollars per share)	$ 21.78
Number outstanding (in shares) | shares	131,000
Weighted Average Remaining Contractual Life of options outstanding (in years)	6 years 2 months 23 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 21.07
Number Exercisable (in shares) | shares	71,004
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 20.65
$22.75 – $27.98 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	22.75
Exercise price, high end of range (in dollars per share)	$ 27.98
Number outstanding (in shares) | shares	133,333
Weighted Average Remaining Contractual Life of options outstanding (in years)	5 years 6 months 4 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 25.14
Number Exercisable (in shares) | shares	93,333
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 24.86
28.29 – $31.40 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	28.29
Exercise price, high end of range (in dollars per share)	$ 31.40
Number outstanding (in shares) | shares	131,500
Weighted Average Remaining Contractual Life of options outstanding (in years)	3 years 7 months 28 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 29.30
Number Exercisable (in shares) | shares	114,000
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 29.29
$31.83 – $32.28 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	31.83
Exercise price, high end of range (in dollars per share)	$ 32.28
Number outstanding (in shares) | shares	98,150
Weighted Average Remaining Contractual Life of options outstanding (in years)	6 years 11 months 16 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 32.11
Number Exercisable (in shares) | shares	42,500
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 31.99
$33.12 – $33.12 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	33.12
Exercise price, high end of range (in dollars per share)	$ 33.12
Number outstanding (in shares) | shares	165,990
Weighted Average Remaining Contractual Life of options outstanding (in years)	9 years 1 month 6 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 33.12
$33.24 – $36.25 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	33.24
Exercise price, high end of range (in dollars per share)	$ 36.25
Number outstanding (in shares) | shares	148,650
Weighted Average Remaining Contractual Life of options outstanding (in years)	8 years 3 months 4 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 35.64
Number Exercisable (in shares) | shares	30,284
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 36.25
$ $36.46 – $38.11 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	36.46
Exercise price, high end of range (in dollars per share)	$ 38.11
Number outstanding (in shares) | shares	129,592
Weighted Average Remaining Contractual Life of options outstanding (in years)	1 year 4 months 6 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 37.90
Number Exercisable (in shares) | shares	119,842
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 38.02
$38.82 – $39.94 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	38.82
Exercise price, high end of range (in dollars per share)	$ 39.94
Number outstanding (in shares) | shares	299,687
Weighted Average Remaining Contractual Life of options outstanding (in years)	4 years 6 months 22 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 39.32
Number Exercisable (in shares) | shares	149,687
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 39.81
$41.37 – $44.97 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	41.37
Exercise price, high end of range (in dollars per share)	$ 44.97
Number outstanding (in shares) | shares	156,200
Weighted Average Remaining Contractual Life of options outstanding (in years)	2 years 3 months 26 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 44.10
Number Exercisable (in shares) | shares	156,200
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 44.10
$45.84 - $50.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	45.84
Exercise price, high end of range (in dollars per share)	$ 50.99
Number outstanding (in shares) | shares	18,500
Weighted Average Remaining Contractual Life of options outstanding (in years)	11 months 1 day
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 48.43
Number Exercisable (in shares) | shares	18,500
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 48.43
$10.42 - $50.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, low end of range (in dollars per share)	10.42
Exercise price, high end of range (in dollars per share)	$ 50.99
Number outstanding (in shares) | shares	1,412,602
Weighted Average Remaining Contractual Life of options outstanding (in years)	5 years 2 months 19 days
Weighted Average Exercise Price of options outstanding (in dollars per share)	$ 34.26
Number Exercisable (in shares) | shares	795,350
Weighted Average Exercise Price of options exercisable (in dollars per share)	$ 35.06