Equity-Based Compensation (Summary Of SAR Activity) (Detail) (USD $)	6 Months Ended
	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at beginning of year	1,702,650
Shares, Granted	0
Shares, Exercised	(49,119)
Shares, Forfeited	(1,663)
Shares, Expired	(12,150)
Shares, Outstanding at end of period	1,639,718
Shares, Exercisable at end of period	1,634,032
Intrinsic value of exercised options	$ 546,203
Weighted-Average Exercise Price, Outstanding at beginning of year	$ 40.43
Weighted-Average Exercise Price, Granted	$ 0.00
Weighted-Average Exercise Price, Exercised	$ 27.05
Weighted-Average Exercise Price, Forfeited	$ 36.36
Weighted-Average Exercise Price, Expired	$ 45.93
Weighted-Average Exercise Price, Outstanding at end of period	$ 40.79
Weighted-Average Exercise Price, Exercisable at end of period	$ 40.87
Stock Option And Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at beginning of year	1,287,724
Shares, Granted	427,621
Shares, Exercised	(37,572)
Shares, Forfeited	(16,606)
Shares, Outstanding at end of period	1,661,167
Shares, Exercisable at end of period	572,231
Intrinsic value of exercised options	$ 573,670
Weighted-Average Exercise Price, Outstanding at beginning of year	$ 28.91
Weighted-Average Exercise Price, Granted	$ 38.52
Weighted-Average Exercise Price, Exercised	$ 22.91
Weighted-Average Exercise Price, Forfeited	$ 33.67
Weighted-Average Exercise Price, Outstanding at end of period	$ 31.47
Weighted-Average Exercise Price, Exercisable at end of period	$ 26.36