Stock Options and Restricted Stock - Narrative (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Aggregate number of shares of common stock issued or transferred under the incentive stock awards plan (in shares)	3,449,854
Stock based compensation expense	$ 21,500,000	$ 14,200,000	$ 10,900,000
Income tax expense benefit resulting from stock options exercised	8,200,000	5,400,000	3,800,000
Excess tax (deductions) benefits included in cash provided by financing activities	$ (665,000)	$ 348,000	$ 1,392,000
Stock options granted (in shares)	634,000	338,000	351,000
Aggregate Intrinsic value of options exercised	$ 400,000	$ 800,000	$ 4,400,000
Fair value of options vested	$ 1,400,000	1,100,000	1,300,000
Employee Service Share-based Compensation, Cash Flow Effect, Cash Used to Settle Awards		$ 0	0
2001 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unexercised options lapse period (in years)	10 years
2015 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unexercised options lapse period (in years)	10 years
Chief Executive Officer
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock based compensation expense			$ 5,100,000
Stock options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized compensation expense related to non-vested award	$ 21,400,000
Unrecognized compensation expense related to non-vested award, recognition period (in years)	1 year 5 months 19 days
Stock options | Minimum | 2001 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	1 year
Stock options | Minimum | 2015 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	1 year
Stock options | Maximum | 2001 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	5 years
Stock options | Maximum | 2015 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	3 years
Restricted Stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock granted (in shares)	379,000	261,000	548,000
Weighted average grant date fair value (in dollars per share)	$ 22.81	$ 31.78	$ 29.11
Total fair value of shares vesting	$ 3,800,000	$ 1,800,000	$ 10,200,000
Restricted Stock | Executive Officer Performance Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	3 years
Restricted Stock | Minimum | 2001 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	1 year
Restricted Stock | Minimum | 2015 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	1 year
Restricted Stock | Minimum | AMP Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	4 years
Restricted Stock | Maximum | 2001 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	5 years
Restricted Stock | Maximum | 2015 Incentive Award Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	3 years
Restricted Stock | Maximum | AMP Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	5 years
Performance Share Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock granted (in shares)	530,000
Weighted average grant date fair value (in dollars per share)	$ 23.19
Total fair value of shares vesting	$ 3,400,000	$ 0	$ 900,000
Performance Share Units | Minimum
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Performance percentage	0.00%
Performance Share Units | Maximum
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Performance percentage	200.00%
Performance criteria is met | Performance Share Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Award vesting rights (percentage)	33.33%
One-year service period | Performance Share Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)	1 year
Award vesting rights (percentage)	33.33%
Award requisite service period (in years)	1 year
Two-year service period | Performance Share Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Award vesting rights (percentage)	33.33%
Award requisite service period (in years)	2 years