Stock-Based Compensation (Details) (USD $)	3 Months Ended			6 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Common-stock based award plan
Number of prior equity plans				1
Compensation expense (in dollars)	$ 5,698,000		$ 4,836,000	$ 11,726,000	$ 8,758,000
Stock options
Common-stock based award plan
The period from the grant date after which options expire				10 years
Compensation expense (in dollars)	2,649,000		2,543,000	6,132,000	5,031,000
Weighted-average assumptions utilized in determining the fair value of options
Risk-free interest rate (as a percent)				0.70%	1.00%
Expected stock volatility (as a percent)				53.87%	53.30%
Dividend yield (as a percent)				1.10%	0.40%
Expected term				5 years 6 months	5 years 6 months
Options
Options outstanding at the beginning of the period (in shares)	4,472,000	4,690,000		4,690,000
Granted (in shares)				364,624
Exercised (in shares)	(164,000)			(745,000)
Forfeited/Expired (in shares)	(2,000)			(4,000)
Option outstanding at the end of the period (in shares)	4,306,000	4,472,000		4,306,000
Vested and expected to vest at the end of the period (in shares)	4,286,000			4,286,000
Exercisable at the end of the period (in shares)	3,376,000			3,376,000
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 33.38	$ 29.56		$ 29.56
Granted (in dollars per share)				$ 54.18
Exercised (in dollars per share)	$ 27.14			$ 18.06
Forfeited/Expired (in dollars per share)	$ 51.86			$ 52.82
Outstanding at the end of the period (in dollars per share)	$ 33.61	$ 33.38		$ 33.61
Vested and expected to vest at the end of the period (in dollars per share)	$ 33.55			$ 33.55
Exercisable at the end of the period (in dollars per share)	$ 28.33			$ 28.33
Weighted- Average Remaining Contractual Term
Outstanding at the end of the period	5 years 3 months 18 days
Vested and expected to vest at the end of the period	5 years 2 months 12 days
Exercisable at the end of the period	4 years 3 months 18 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	116,700,000			116,700,000
Vested and expected to vest at the end of the period (in dollars)	116,400,000			116,400,000
Exercisable at the end of the period (in dollars)	109,300,000			109,300,000
Weighted-average fair value of options granted (in dollars per share)	$ 0.00	$ 23.80
Total intrinsic value of options exercised (in dollars)	4,400,000			13,400,000
Unrecognized compensation cost (in dollars)	14,700,000			14,700,000
Weighted-average period over which unrecognized compensation cost is expected to be recognized				2 years 9 months 18 days
Restricted stock
Common-stock based award plan
Compensation expense (in dollars)	3,049,000		2,293,000	5,594,000	3,727,000
Aggregate Intrinsic Value
Unrecognized compensation cost (in dollars)	$ 23,800,000			$ 23,800,000
Weighted-average period over which unrecognized compensation cost is expected to be recognized				3 years 2 months 12 days
Restricted stock awards activity, shares
Unvested at the beginning of the period (in shares)		430,000		430,000
Granted (in shares)				307,100
Vested (in shares)				(155,000)
Forfeited (in shares)				(2,000)
Unvested at the end of the period (in shares)	580,000			580,000
Restricted stock awards activity, weighted average grant date fair value
Unvested at the beginning of the period (in dollars per share)		$ 52.52		$ 52.52
Granted (in dollars per share)				$ 54.18
Vested (in dollars per share)				$ 45.88
Forfeited (in dollars per share)				$ 55.38
Unvested at the end of the period (in dollars per share)	$ 55.17			$ 55.17
Restricted stock | Minimum
Aggregate Intrinsic Value
Vesting period				3 years
Restricted stock | Maximum
Aggregate Intrinsic Value
Vesting period				6 years