Pension Plan and Retirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended						3 Months Ended	12 Months Ended												1 Months Ended		12 Months Ended
	Jan. 31, 2007	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2012 Defined Benefit Pension Plans	Sep. 30, 2011 Defined Benefit Pension Plans	Sep. 30, 2010 Defined Benefit Pension Plans	Dec. 31, 2007 U.S. pension plan	Sep. 30, 2012 U.S. pension plan	Sep. 30, 2011 U.S. pension plan	Sep. 30, 2010 U.S. pension plan	Sep. 30, 2012 U.K. pension plan	Sep. 30, 2011 U.K. pension plan	Sep. 30, 2010 U.K. pension plan	Sep. 30, 2009 U.K. pension plan	Sep. 30, 2012 U.K. pension plan U.K. subsidiary	Sep. 30, 2011 U.K. pension plan U.K. subsidiary	Sep. 30, 2012 Non-qualified pension plan	Sep. 30, 2011 Non-qualified pension plan	Sep. 30, 2010 Non-qualified pension plan	Jan. 31, 2007 Postretirement Health Care Benefits	Mar. 31, 2006 Postretirement Health Care Benefits	Sep. 30, 2012 Postretirement Health Care Benefits	Sep. 30, 2011 Postretirement Health Care Benefits	Sep. 30, 2010 Postretirement Health Care Benefits	Sep. 30, 2012 Postretirement Health Care Benefits Over 65 age group	Sep. 30, 2011 Postretirement Health Care Benefits Over 65 age group	Sep. 30, 2012 Postretirement Health Care Benefits Under 65 age group	Sep. 30, 2011 Postretirement Health Care Benefits Under 65 age group
Pension Plan and Retirement Benefits
Percentage of employee's contribution contributed by the company for all employees except for all salaried employees and certain hourly employees		50.00%
Maximum percentage of employee's salary that can be contributed by the company for all employees except for all salaried employees and certain hourly employees		3.00%
Percentage of employee's contribution contributed by the company for all salaried employees and certain hourly employees		60.00%
Maximum percentage of employee's salary that can be contributed by the company for all salaried employees and certain hourly employees		6.00%
Expenses associated with defined contribution plan (401(k))		$ 1,374	$ 1,273	$ 990
Defined Benefit Plans
Pension multiplier before increase (as a percent)									1.40%
Pension multiplier after increase (as a percent)									1.60%
Reduction in projected benefit obligation								8,191							392
Increase to other comprehensive income (before tax)								4,532							392
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments								3,659
Maximum liability related to total retiree health care costs under plan amendment	5,000				5,000																5,000
Reduction in accumulated postretirement benefit liability due to plan amendment																						46,313
Period of amortization as a reduction to expense																						8 years
Change in Benefit Obligation:
Projected benefit obligation at beginning of year					261,953	239,006																	101,515	98,624
Service cost					4,001	3,612	3,596																291	266	206
Interest cost					11,623	11,383	11,600																4,581	4,688	4,819
Actuarial losses					38,147	19,833																	11,974	2,662
Benefits paid					(12,279)	(11,881)																	(4,152)	(4,725)
Projected benefit obligation at end of year					303,445	261,953	239,006																114,209	101,515	98,624
Change in Plan Assets:
Fair value of plan assets at beginning of year					148,931	144,976			135,723			13,208
Actual return on assets					28,489	2,181
Employer contribution					16,870	13,655			15,900	12,720						970	935						4,152	4,725
Benefits paid					(12,279)	(11,881)																	(4,152)	(4,725)
Fair value of plan assets at end of year					182,011	148,931	144,976		166,285	135,723		15,726	13,208
Funded Status of Plan:
Unfunded status					(121,434)	(113,022)																	(114,209)	(101,515)
Amounts recognized in the consolidated balance sheets
Accrued pension and postretirement benefits		(236,552)	(215,432)		(121,434)	(113,022)												(909)	(895)				(114,209)	(101,515)
Accumulated other comprehensive loss		160,742	134,204		120,794	109,221																	39,948	24,983
Amounts expected to be recognized from AOCI into the statement of operations in the following year:
Amortization of net loss		13,906	11,830		10,189	9,031																	3,717	2,799
Amortization of unrecognized prior service cost		(4,981)	(4,981)		808	808	808																(5,789)	(5,789)	(5,789)
Total		8,925	6,849		10,997	9,839																	(2,072)	(2,990)
Accumulated benefit obligation		281,623	245,197
Components of net periodic pension cost and postretirement health care benefit cost
Service cost					4,001	3,612	3,596																291	266	206
Interest cost					11,623	11,383	11,600																4,581	4,688	4,819
Expected return on assets					(11,755)	(12,023)	(10,626)
Amortization of prior service cost					808	808	808																(5,789)	(5,789)	(5,789)
Recognized actuarial loss					9,031	6,285	4,922																2,799	2,706	1,992
Net periodic cost					13,708	10,065	10,300											110	84	109			1,882	1,871	1,228
Assumptions relating to health care cost trend rates
Annual rate of increase for the costs of covered health care benefits on the basis of age (as a percent)																										5.50%	6.00%	6.50%	7.00%
Ultimate annual rate of decrease in costs of covered health care benefits by year 2016 (as a percent)																							5.00%	5.00%
Assumptions
Discount rate (as a percent)									3.625%	4.50%		4.10%	5.20%										3.875%	4.625%
Rate of compensation increase (as a percent)					3.50%	3.50%
Assumptions used to determine net periodic benefit cost
Discount rate (as a percent)									4.50%	4.875%	5.50%	5.20%	5.00%	5.50%									4.625%	4.875%	5.50%
Expected return on plan assets (as a percent)									8.00%	8.50%	8.50%	5.90%	5.90%	6.20%
Rate of compensation increase (as a percent)									3.50%	3.50%	4.00%
Effect of one percentage point change in assumed health care cost trend rates
Effect on total of service and interest cost components of one percent increase		0
Effect on total of service and interest cost components of one percent decrease		0
Effect on accumulated postretirement benefit obligation of one percent increase		0
Effect on accumulated postretirement benefit obligation of one percent decrease		$ 0