Benefit Plans - Options Outstanding and Options Exercisable by Exercise Price with Weighted-Average Remaining Contractual Life for Options Outstanding and Weighted-Average Exercise Price (Detail)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Exercise Price 15-20 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Lower Range Limit	$ 15
Exercise Price Upper Range Limit	$ 20
Options Outstanding, Number | shares	2,400
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	2 months 1 day
Options Outstanding, Weighted-Average Grant Date Value	$ 15.62
Options Exercisable, Number | shares	2,400
Options Exercisable, Weighted-Average Grant Date Value	$ 15.62
Exercise Price 20-25 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Lower Range Limit	20
Exercise Price Upper Range Limit	$ 25
Options Outstanding, Number | shares	153,855
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	1 year 2 months 19 days
Options Outstanding, Weighted-Average Grant Date Value	$ 23.86
Options Exercisable, Number | shares	151,965
Options Exercisable, Weighted-Average Grant Date Value	$ 23.86
Exercise Price 25-30 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Lower Range Limit	25
Exercise Price Upper Range Limit	$ 30
Options Outstanding, Number | shares	508,795
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	2 years 15 days
Options Outstanding, Weighted-Average Grant Date Value	$ 28.98
Options Exercisable, Number | shares	424,960
Options Exercisable, Weighted-Average Grant Date Value	$ 29.01
Exercise Price 30-35 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Lower Range Limit	30
Exercise Price Upper Range Limit	$ 35
Options Outstanding, Number | shares	736,200
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5 years 7 months 2 days
Options Outstanding, Weighted-Average Grant Date Value	$ 32.04
Options Exercisable, Number | shares	79,480
Options Exercisable, Weighted-Average Grant Date Value	$ 32.62
Exercise Price 35-40 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Lower Range Limit	35
Exercise Price Upper Range Limit	$ 40
Options Outstanding, Number | shares	9,400
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	4 years 11 months 16 days
Options Outstanding, Weighted-Average Grant Date Value	$ 37.83
Options Exercisable, Number | shares	3,540
Options Exercisable, Weighted-Average Grant Date Value	$ 37.90
Exercise Price 15-40 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Lower Range Limit	15
Exercise Price Upper Range Limit	$ 40
Options Outstanding, Number | shares	1,410,650
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	3 years 9 months 26 days
Options Outstanding, Weighted-Average Grant Date Value	$ 29.91
Options Exercisable, Number | shares	662,345
Options Exercisable, Weighted-Average Grant Date Value	$ 27.53