Stock Options and Restricted Stock - Narrative (Detail) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2015 USD ($) period $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares
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 | shares		4,802,248
Stock based compensation expense		$ 14,200	$ 10,900	$ 2,300
Income tax expense benefit resulting from stock options exercised		5,400	3,800	889
Excess tax benefits included in cash provided by financing activities		$ 348	$ 1,392	$ 1,381
Stock options granted (in shares) | shares		338,000	351,000	0
Aggregate Intrinsic value of options exercised		$ 844	$ 4,400	$ 11,000
Fair value of options vested		$ 1,100	1,300	$ 2,700
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
Stock options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized compensation expense related to non-vested award		$ 23,900
Unrecognized compensation expense related to non-vested award, recognition period (in years)		1 year 7 months 6 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) | shares		261,000	548,000	307,000
Weighted average grant date fair value (in dollars per share) | $ / shares		$ 31.78	$ 29.11	$ 29.23
Nonvested shares subject to performance condition | shares	[1]	37,500
Total fair value of shares vesting		$ 1,800	$ 11,100	$ 184
Restricted Stock | Executive Officer Performance Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Vesting period (in years)		3 years
Number of annual performance periods | period		3
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) | shares		358,000
Weighted average grant date fair value (in dollars per share) | $ / shares		$ 32.03
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%
Immediately | 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

[1] The outstanding non-vested restricted stock as of December 31, 2015 includes 37,500 shares that are subject to performance conditions.