Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term of stock options granted under the plan (in years)	10
Vesting period, generally, for stock options granted under the plan (in years)	3
Share based compensation costs	$ 2,700,000	$ 2,000,000	$ 2,200,000
Tax benefit of share-based compensation	1,100,000	800,000	900,000
Weighted Average Remaining Contractual Life [Abstract]
Outstanding options, end of year (in years)	5.71
Exercisable options, end of year (in years)	4.63
Aggregate Intrinsic Value [Abstract]
Outstanding options, end of year	10,087,000
Exercisable options, end of year	2,639,000
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	$ 38.620
Exercise price range, upper limit	$ 69.315
Options Outstanding [Abstract]
Number outstanding at end of period (in shares)	786,987
Weighted average remaining contractual term (in years)	5.2
Weighted average exercise price (in dollars per share)	$ 54.19
Options Exercisable [Abstract]
Number exercisable at end of period (in shares)	559,670
Weighted average exercise price (in dollars per share)	$ 54.15
$34.825 to $44.360 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	$ 38.620
Exercise price range, upper limit	$ 49.505
Options Outstanding [Abstract]
Number outstanding at end of period (in shares)	302,241
Weighted average remaining contractual term (in years)	6.4
Weighted average exercise price (in dollars per share)	$ 44.69
Options Exercisable [Abstract]
Number exercisable at end of period (in shares)	183,199
Weighted average exercise price (in dollars per share)	$ 44.24
$46.625 to $54.225 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	$ 50.785
Exercise price range, upper limit	$ 59.330
Options Outstanding [Abstract]
Number outstanding at end of period (in shares)	158,162
Weighted average remaining contractual term (in years)	2.8
Weighted average exercise price (in dollars per share)	$ 54.09
Options Exercisable [Abstract]
Number exercisable at end of period (in shares)	154,402
Weighted average exercise price (in dollars per share)	$ 54.09
$55.870 to $69.315 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	$ 60.195
Exercise price range, upper limit	$ 69.315
Options Outstanding [Abstract]
Number outstanding at end of period (in shares)	326,584
Weighted average remaining contractual term (in years)	6.5
Weighted average exercise price (in dollars per share)	$ 63.04
Options Exercisable [Abstract]
Number exercisable at end of period (in shares)	222,069
Weighted average exercise price (in dollars per share)	$ 62.38
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeiture rate assumed (in hundredths)	6.87%
Weighted average grant date fair value for stock options granted (in dollars per share)	$ 22.06	$ 16.32	$ 11.86
Weighted average grant date fair value for stock options vested (in dollars per share)	$ 15.17	$ 17.01	$ 20.15
Total intrinsic value of stock options exercised	1,700,000	500,000	100,000
Expected life (years)	6.3	6.3	6.3
Interest rate (in hundredths)	2.46%	2.92%	1.87%
Volatility (in hundredths)	30.93%	28.80%	28.01%
Expected dividend yield (in hundredths)	0.31%	0.41%	0.50%
Stock Options [Roll Forward]
Balance, beginning of year (in shares)	820,030	787,530	661,781
Granted (in shares)	122,323	141,140	179,200
Exercised (in shares)	(120,598)	(31,697)	(7,532)
Forfeited/canceled (in shares)	(34,768)	(76,943)	(45,919)
Balance, end of year (in shares)	786,987	820,030	787,530
Exercisable, end of year (in shares)	559,670
Weighted Average Exercise Price Per Share [Abstract]
Balance, beginning of year (in dollars per share)	$ 52.11
Granted (in dollars per share)	$ 64.12
Exercised (in dollars per share)	$ 50.02
Forfeited/canceled (in dollars per share)	$ 53.59
Balance, end of year (in dollars per share)	$ 54.19	$ 52.11
Exercisable, end of year (in dollars per share)	$ 54.16
Aggregate Intrinsic Value [Abstract]
Closing stock price on last business day of the period (in dollars per share)	$ 56.53
Weighted average intrinsic value of options exercised (in dollars per share)	$ 14.30	$ 16.06	$ 18.50
Unrecognized stock-based compensation expense	1,500,000
Weighted average period over which unrecognized stock-based compensation expense is expected to be recognized (in years)	3
Restricted Stock [Roll Forward]
Balance, beginning of year (in shares)	820,030
Granted (in shares)	122,323
Vested (in shares)	(120,598)
Canceled (in shares)	(34,768)
Balance, end of year (in shares)	786,987	820,030
Weighted Average Grant Date Fair Value [Abstract]
Balance, beginning of year (in dollars per share)	$ 52.11	$ 52.54	$ 55.14
Granted (in dollars per share)	$ 64.12	$ 49.12	$ 39.84
Vested (in dollars per share)	$ 50.02	$ 44.88	$ 35.63
Canceled (in dollars per share)	$ 53.59	$ 54.42	$ 43.14
Balance, end of year (in dollars per share)	$ 54.19	$ 52.11	$ 52.54
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation costs	4,600,000	3,800,000	4,200,000
Stock Options [Roll Forward]
Balance, beginning of year (in shares)	150,270	188,718	161,294
Granted (in shares)	68,489	78,320	101,400
Exercised (in shares)	(47,123)	(59,087)	(41,020)
Forfeited/canceled (in shares)	(45,624)	(57,681)	(32,956)
Balance, end of year (in shares)	126,012	150,270	188,718
Weighted Average Exercise Price Per Share [Abstract]
Balance, beginning of year (in dollars per share)	$ 47.19	$ 50.16	$ 61.63
Granted (in dollars per share)	$ 64.17	$ 49.13	$ 39.65
Exercised (in dollars per share)	$ 63.98	$ 54.43	$ 60.35
Forfeited/canceled (in dollars per share)	$ 60.44	$ 52.12	$ 61.30
Balance, end of year (in dollars per share)	$ 54.42	$ 47.19	$ 50.16
Aggregate Intrinsic Value [Abstract]
Unrecognized stock-based compensation expense	2,700,000
Weighted average period over which unrecognized stock-based compensation expense is expected to be recognized (in years)	3
Weighted Average Grant Date Fair Value [Abstract]
Reversals of compensation expense related to restricted stock forfeitures	$ 100,000	$ 100,000	$ 600,000
Nonvested Stock Options [Member]
Stock Options [Roll Forward]
Balance, beginning of year (in shares)	269,315
Granted (in shares)	122,323
Vested (in shares)	(133,864)
Forfeited/canceled (in shares)	(30,457)
Balance, end of year (in shares)	227,317
Weighted Average Exercise Price Per Share [Abstract]
Balance, beginning of year (in dollars per share)	$ 47.13
Granted (in dollars per share)	$ 64.12
Vested (in dollars per share)	$ 48.76
Forfeited/canceled (in dollars per share)	$ 54.78
Balance, end of year (in dollars per share)	$ 54.29