Share-Based Plans (Summary of Restricted Stock and Stock Option Activity) (Detail) - $ / shares		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options granted, Number of Shares		377,598	0
Options exercised, Number of Shares		(58,473)
Options exercisable, at end of period, Number of Shares		1,420,758
Options expected to vest, at end of period, Number of Shares		105,378
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Options exercisable, at end of period, Weighted-Average Exercise Price (in dollars per share)		$ 23.99
Options expected to vest, at end of period, Weighted-Average Exercise Price (in dollars per share)		$ 23.00
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Restricted stock, Outstanding at beginning of period (in shares)		243,015
Restricted stock, Granted (in shares)		223,190
Restricted stock, Vested restricted stock awards (in shares)	[1]	(220,866)
Restricted stock, Forfeited (in shares)		(9,194)
Restricted stock, Outstanding at end of period (in shares)		236,145	243,015
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Restricted stock, at beginning of period, Weighted-average Grant Date Fair Value (in dollars per share)		$ 27.03
Restricted stock, Granted (in dollars per share)		34.82
Restricted stock, Vested restricted stock awards (in dollars per share)	[1]	28.83
Restricted stock, Forfeited (in dollars per share)		30.27
Restricted stock, at end of period, Weighted-average Grant Date Fair Value (in dollars per share)		$ 32.58	$ 27.03
Time Based Restricted Stock Unit Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Restricted stock, Outstanding at beginning of period (in shares)		2,279
Restricted stock, Granted (in shares)		12,531
Restricted stock, Vested restricted stock awards (in shares)	[1]	(12,722)
Restricted stock, Forfeited (in shares)		0
Restricted stock, Outstanding at end of period (in shares)		2,088	2,279
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Restricted stock, at beginning of period, Weighted-average Grant Date Fair Value (in dollars per share)		$ 29.34
Restricted stock, Granted (in dollars per share)		34.45
Restricted stock, Vested restricted stock awards (in dollars per share)	[1]	33.53
Restricted stock, Forfeited (in dollars per share)		0.00
Restricted stock, at end of period, Weighted-average Grant Date Fair Value (in dollars per share)		$ 34.45	$ 29.34
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Restricted stock, Outstanding at beginning of period (in shares)		130,193
Restricted stock, Granted (in shares)		138,591
Restricted stock, Vested restricted stock awards (in shares)	[1]	(153,063)
Restricted stock, Forfeited (in shares)		0
Restricted stock, Outstanding at end of period (in shares)		115,721	130,193
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Restricted stock, at beginning of period, Weighted-average Grant Date Fair Value (in dollars per share)		$ 28.61
Restricted stock, Granted (in dollars per share)		36.15
Restricted stock, Vested restricted stock awards (in dollars per share)	[1]	31.27
Restricted stock, Forfeited (in dollars per share)		0.00
Restricted stock, at end of period, Weighted-average Grant Date Fair Value (in dollars per share)		$ 34.14	$ 28.61
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, at beginning of period, Number of Shares		1,900,144
Options granted, Number of Shares		0
Options exercised, Number of Shares		(221,320)
Options forfeited, Number of Shares		(151,750)
Options outstanding, at end of period, Number of Shares		1,527,074	1,900,144
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Options, at beginning of period, Weighted-average Exercise Price (in dollars per share)		$ 24.95
Options granted, Weighted-Average Exercise Price (in dollars per share)		0.00
Options exercised, Weighted-Average Exercise Price (in dollars per share)		18.09
Options forfeited, Weighted-Average Exercise Price (in dollars per share)		45.36
Options, at end of period, Weighted-average Exercise Price (in dollars per share)		$ 23.92	$ 24.95

[1] Vested for purposes of recording compensation expense.