Stock Compensation Plans (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Stock Compensation Plans [Abstract]
Number of stock compensation plans	2		2
Compensation Expense [Abstract]
Share-based compensation expense	$ 1,784,000	$ 115,000	$ 5,200,000	$ 2,987,000
Tax benefit	(660,000)	(43,000)	(1,924,000)	(1,105,000)
Stock-based compensation expense, net of tax	1,124,000	72,000	3,276,000	1,882,000
Restricted Stock [Member] | Granted to Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	2,700,000		2,700,000
Weighted-average period of cost recognition (in years)			1.64
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period, minimum (in years)			2
Vesting period, maximum (in years)			4
Unrecognized compensation expense	11,200,000		11,200,000
Weighted-average period of cost recognition (in years)			1.75
Valuation Assumptions [Abstract]
Expected dividend yield, maximum (in hundredths)			0.67%	0.80%
Expected dividend yield, minimum (in hundredths)			0.64%	0.60%
Expected stock price volatility, minimum (in hundredths)			45.00%	40.50%
Expected stock price volatility, maximum (in hundredths)			56.40%	57.90%
Risk free interest rate, minimum (in hundredths)			0.27%	0.28%
Risk free interest rate, maximum (in hundredths)			0.82%	2.39%
Expected life options, minimum (in years)			2	2
Expected life options, maximum (in years)			4	5
Weighted-average fair value per share at grant date (in dollars per share)			$ 24.54	$ 27.41
Stock Options, Shares [Roll Forward]
Outstanding, beginning of period (in shares)			1,504,311
Granted (in shares)			13,500
Exercised (in shares)			(66,151)
Forfeited or expired (in shares)			(22,724)
Outstanding, end of period (in shares)	1,428,936		1,428,936
Exercisable, end of period (in shares)	706,738		706,738
Weighted-Average Exercise Price [Abstract]
Outstanding, beginning of period (in dollars per share)			$ 42.26
Granted (in dollars per share)	$ 75.75		$ 75.75
Exercised (in dollars per share)	$ 27.54		$ 27.54
Forfeited or expired (in dollars per share)			$ 46.00
Outstanding, end of period (in dollars per share)	$ 43.20		$ 43.20
Exercisable, end of period (in dollars per share)	$ 35.99		$ 35.99
Weighted-Average Remaining Contractual Term [Abstract]
Outstanding, end of period (in years)	7.2		7.2
Exercisable, end of period (in years)			6.2
Aggregate Intrinsic Value [Abstract]
Outstanding, end of period	19,307,000		19,307,000
Exercisable, end of period	14,112,000		14,112,000
Intrinsic value of stock options exercised			$ 3,200,000
Stock Options [Member] | Granted to Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration term (in years)			10
Stock Options [Member] | Granted to Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration term (in years)			10