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, 2016 $ / shares shares
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	751,500
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	6 years 11 months 23 days
Options Outstanding, Weighted-Average Grant Date Value	$ 24.60
Options Exercisable, Number | shares	3,780
Options Exercisable, Weighted-Average Grant Date Value	$ 23.84
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	171,920
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	4 years 29 days
Options Outstanding, Weighted-Average Grant Date Value	$ 28.59
Options Exercisable, Number | shares	118,500
Options Exercisable, Weighted-Average Grant Date Value	$ 28.93
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	651,355
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5 years 10 months 6 days
Options Outstanding, Weighted-Average Grant Date Value	$ 32.06
Options Exercisable, Number | shares	231,005
Options Exercisable, Weighted-Average Grant Date Value	$ 32.12
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	9,600
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	6 years 4 months 28 days
Options Outstanding, Weighted-Average Grant Date Value	$ 38.43
Options Exercisable, Number | shares	880
Options Exercisable, Weighted-Average Grant Date Value	$ 36.62
Exercise Price 20-40 [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	$ 40
Options Outstanding, Number | shares	1,584,375
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	6 years 2 months 12 days
Options Outstanding, Weighted-Average Grant Date Value	$ 28.14
Options Exercisable, Number | shares	354,165
Options Exercisable, Weighted-Average Grant Date Value	$ 30.78