Stock-Based Compensation Plans (Summary Of Restricted Stock Activity) (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013		Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Options outstanding, at end of period, Weighted-Average Exercise Price (in dolars per share)	$ 27.93		$ 27.93
Time Based Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Restricted stock, at beginning of period, Number of Shares	373,247		249,294
Restricted stock, at beginning of period, Weighted-average Grant Date Fair Value (in dolars per share)	$ 22.31		$ 22.12
Granted, Number of Shares	33,665		211,274
Granted, Weighted-average Grant Date Fair Value (in dolars per share)	$ 22.96		$ 22.60
Vested, Number of Shares	53,998	[1]	100,498	[1]
Vested, Weighted-average Grant Date Fair Value (in dolars per share)	$ 22.29	[1]	$ 22.22	[1]
Forfetied/Modified Number of Shares	4,160		11,316
Forfeited/Modified Weighted-average Grant Date Fair Value (in dollars per share)	$ 22.53		$ 22.25
Restricted stock, at end of period, Number of Shares	348,754		348,754
Options outstanding, at end of period, Weighted-Average Exercise Price (in dolars per share)	$ 22.38		$ 22.38
Performance Based Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Restricted stock, at beginning of period, Number of Shares	240,536		94,407
Restricted stock, at beginning of period, Weighted-average Grant Date Fair Value (in dolars per share)	$ 24.52		$ 25.44
Granted, Number of Shares	0		163,519
Granted, Weighted-average Grant Date Fair Value (in dolars per share)	$ 0.00		$ 24.04
Vested, Number of Shares	24,748	[1]	40,619	[1]
Vested, Weighted-average Grant Date Fair Value (in dolars per share)	$ 24.67	[1]	$ 24.81	[1]
Forfetied/Modified Number of Shares	0		1,519
Forfeited/Modified Weighted-average Grant Date Fair Value (in dollars per share)	$ 0.00		$ 25.47
Restricted stock, at end of period, Number of Shares	215,788		215,788
Options outstanding, at end of period, Weighted-Average Exercise Price (in dolars per share)	$ 24.50		$ 24.50
Time Based Restricted Stock Unit Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Restricted stock, at beginning of period, Number of Shares	26,884		33,742
Restricted stock, at beginning of period, Weighted-average Grant Date Fair Value (in dolars per share)	$ 22.11		$ 22.12
Vested, Number of Shares	6,857	[1]	13,715	[1]
Vested, Weighted-average Grant Date Fair Value (in dolars per share)	$ 22.17	[1]	$ 22.17	[1]
Restricted stock, at end of period, Number of Shares	20,027		20,027
Options outstanding, at end of period, Weighted-Average Exercise Price (in dolars per share)	$ 22.09		$ 22.09

[1] Vested for purposes of recording compensation expense on a straight-line basis.