Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
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	$ 2,000,000	$ 2,700,000	$ 2,000,000
Tax benefit of share-based compensation	800,000	1,100,000	800,000
Weighted Average Grant Date Fair Value [Abstract]
Reversals of compensation expense related to restricted stock forfeitures	0
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	$ 19.855
Exercise price range, upper limit	$ 34.657
Options Outstanding [Abstract]
Number outstanding at end of period (in shares)	1,395,520
Weighted average remaining contractual term (in years)	4.0
Weighted average exercise price (in dollars per share)	$ 28.31
Options Exercisable [Abstract]
Number exercisable at end of period (in shares)	1,068,434
Weighted average exercise price (in dollars per share)	$ 27.44
$19.855 to $24.753 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	$ 19.855
Exercise price range, upper limit	$ 24.753
Options Outstanding [Abstract]
Number outstanding at end of period (in shares)	413,026
Weighted average remaining contractual term (in years)	3.5
Weighted average exercise price (in dollars per share)	$ 22.14
Options Exercisable [Abstract]
Number exercisable at end of period (in shares)	376,530
Weighted average exercise price (in dollars per share)	$ 21.90
$26.257 to $29.665 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	$ 26.257
Exercise price range, upper limit	$ 29.665
Options Outstanding [Abstract]
Number outstanding at end of period (in shares)	153,718
Weighted average remaining contractual term (in years)	2.1
Weighted average exercise price (in dollars per share)	$ 27.08
Options Exercisable [Abstract]
Number exercisable at end of period (in shares)	148,706
Weighted average exercise price (in dollars per share)	$ 27.08
$30.097 to $34.657 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	$ 30.097
Exercise price range, upper limit	$ 34.657
Options Outstanding [Abstract]
Number outstanding at end of period (in shares)	828,776
Weighted average remaining contractual term (in years)	6.3
Weighted average exercise price (in dollars per share)	$ 31.61
Options Exercisable [Abstract]
Number exercisable at end of period (in shares)	543,198
Weighted average exercise price (in dollars per share)	$ 31.37
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeiture rate assumed (in hundredths)	7.31%
Weighted average grant date fair value for stock options granted (in dollars per share)	$ 10.74	$ 11.03	$ 8.16
Weighted average grant date fair value for stock options vested (in dollars per share)	$ 8.57	$ 7.58	$ 8.50
Total intrinsic value of stock options exercised	3,300,000	1,700,000	500,000
Expected life (years)	6.9	6.3	6.3
Interest rate (in hundredths)	1.36%	2.46%	2.92%
Volatility (in hundredths)	31.26%	30.93%	28.80%
Expected dividend yield (in hundredths)	0.31%	0.31%	0.41%
Stock Options [Roll Forward]
Balance, beginning of year (in shares)	1,573,974	1,640,060	1,575,060
Granted (in shares)	222,250	244,646	282,280
Exercised (in shares)	(330,158)	(241,196)	(63,394)
Forfeited/canceled (in shares)	(70,546)	(69,536)	(153,886)
Balance, end of year (in shares)	1,395,520	1,573,974	1,640,060
Exercisable, end of year (in shares)	1,068,434
Weighted Average Exercise Price Per Share [Abstract]
Balance, beginning of year (in dollars per share)	$ 27.10	$ 27.05	$ 26.27
Granted (in dollars per share)	$ 32.04	$ 32.06	$ 24.56
Exercised (in dollars per share)	$ 25.15	$ 25.01	$ 22.44
Forfeited/canceled (in dollars per share)	$ 27.76	$ 26.80	$ 27.21
Balance, end of year (in dollars per share)	$ 28.31	$ 27.10	$ 27.05
Exercisable, end of year (in dollars per share)	$ 27.44
Weighted Average Remaining Contractual Life [Abstract]
Outstanding options, end of year (in years)	5.93
Exercisable options, end of year (in years)	5.11
Aggregate Intrinsic Value [Abstract]
Outstanding options, end of year	16,201,000
Exercisable options, end of year	13,337,000
Closing stock price on last business day of the period (in dollars per share)	$ 39.92
Weighted average intrinsic value of options exercised (in dollars per share)	$ 10.11	$ 7.15	$ 8.03
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 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation costs	3,400,000	4,600,000	3,800,000
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
Restricted Stock [Roll Forward]
Balance, beginning of year (in shares)	252,024	300,540	377,436
Granted (in shares)	123,446	136,978	156,640
Vested (in shares)	(102,424)	(94,246)	(118,174)
Canceled (in shares)	(89,386)	(91,248)	(115,362)
Balance, end of year (in shares)	183,660	252,024	300,540
Weighted Average Grant Date Fair Value [Abstract]
Balance, beginning of year (in dollars per share)	$ 27.21	$ 23.60	$ 25.08
Granted (in dollars per share)	$ 32.04	$ 32.08	$ 24.57
Vested (in dollars per share)	$ 25.90	$ 31.99	$ 27.22
Canceled (in dollars per share)	$ 27.08	$ 30.22	$ 26.06
Balance, end of year (in dollars per share)	$ 31.25	$ 27.21	$ 23.60
Reversals of compensation expense related to restricted stock forfeitures		$ 100,000	$ 100,000
Nonvested Stock Options [Member]
Stock Options [Roll Forward]
Balance, beginning of year (in shares)	454,634
Granted (in shares)	222,250
Vested (in shares)	(311,152)
Forfeited/canceled (in shares)	(38,646)
Balance, end of year (in shares)	327,086
Weighted Average Exercise Price Per Share [Abstract]
Balance, beginning of year (in dollars per share)	$ 27.14
Granted (in dollars per share)	$ 32.04
Vested (in dollars per share)	$ 25.98
Forfeited/canceled (in dollars per share)	$ 30.63
Balance, end of year (in dollars per share)	$ 31.17