Stock-Based Compensation (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Mar. 31, 2012 Y	Dec. 31, 2011	Mar. 31, 2011	Mar. 31, 2012 Y	Mar. 31, 2011 Y
Common-stock based award plan
Compensation expense (in dollars)	$ 4,836,000		$ 2,957,000	$ 8,758,000	$ 6,144,000
Stock options
Common-stock based award plan
The period from the grant date after which options expire (in years)				P10Y
Compensation expense (in dollars)	2,543,000		1,698,000	5,031,000	3,813,000
Weighted-average assumptions utilized in determining the fair value of options
Risk-free interest rate (as a percent)				1.00%	1.90%
Expected stock volatility (as a percent)				53.30%	51.60%
Dividend yield (as a percent)				0.40%	0.50%
Expected term (in years)				5.5	5.5
Options
Options outstanding at the beginning of the period (in shares)	4,814	4,589		4,589
Granted (in shares)				453
Exercised (in shares)	(75)			(280)
Forfeited/Expired (in shares)				(23)
Option outstanding at the end of the period (in shares)	4,739	4,814		4,739
Vested and expected to vest at the end of the period (in shares)	4,681			4,681
Exercisable at the end of the period (in shares)	3,606			3,606
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 29.45	$ 25.84		$ 25.84
Granted (in dollars per share)	$ 59.76			$ 59.76
Exercised (in dollars per share)	$ 21.59			$ 16.61
Forfeited/Expired (in dollars per share)				$ 36.10
Outstanding at the end of the period (in dollars per share)	$ 29.58	$ 29.45		$ 29.58
Vested and expected to vest at the end of the period (in dollars per share)	$ 28.94			$ 28.94
Exercisable at the end of the period (in dollars per share)	$ 24.63			$ 24.63
Weighted- Average Remaining Contractual Term (in years)
Outstanding at the end of the period (in years)	5.3			5.3
Vested and expected to vest at the end of the period (in years)	5.3
Exercisable at the end of the period (in years)	4.3
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	118,100,000			118,100,000
Vested and expected to vest at the end of the period (in dollars)	117,100,000			117,100,000
Exercisable at the end of the period (in dollars)	105,800,000			105,800,000
Weighted-average fair value of options granted (in dollars per share)		$ 27.75
Total intrinsic value of options exercised (in dollars)	3,100,000			11,200,000
Unrecognized compensation cost (in dollars)	17,000,000			17,000,000
Period over which unrecognized compensation cost is expected to be recognized (in years)				3.0
Restricted stock
Common-stock based award plan
Compensation expense (in dollars)	2,293,000		1,259,000	3,727,000	2,331,000
Aggregate Intrinsic Value
Unrecognized compensation cost (in dollars)	$ 18,100,000			$ 18,100,000
Period over which unrecognized compensation cost is expected to be recognized (in years)				3.1
Vesting period, minimum (in years)				P3Y
Vesting period, maximum (in years)				P6Y
Restricted stock awards activity, shares
Unvested at the beginning of the period (in shares)		323		323
Granted (in shares)				244
Vested (in shares)				(119)
Forfeited (in shares)				(7)
Unvested at the end of the period (in shares)	441			441
Restricted stock awards activity, weighted average grant date fair value
Unvested at the beginning of the period (in dollars per share)		$ 42.38		$ 42.38
Granted (in dollars per share)				$ 59.76
Vested (in dollars per share)				$ 40.21
Forfeited (in dollars per share)	$ 41.93			$ 41.93
Unvested at the end of the period (in dollars per share)	$ 52.59			$ 52.59