Pension and Post-retirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Defined Benefit Pension Plans
Pension Plan and Retirement Benefits
Service cost	$ 1,020	$ 974	$ 2,040	$ 1,949
Interest cost	2,865	2,582	5,713	5,223
Expected return	(3,399)	(3,483)	(6,775)	(7,046)
Amortizations	2,385	1,355	4,766	2,716
Net periodic benefit cost	2,871	1,428	5,744	2,842
U.S. pension plan
Pension Plan and Retirement Benefits
Employer contribution			3,000
Expected future employer contribution			3,000
U.K. pension plan
Pension Plan and Retirement Benefits
Employer contribution			439
Expected future employer contribution			243
Postretirement Health Care Benefits
Pension Plan and Retirement Benefits
Service cost	58	85	116	169
Interest cost	1,149	1,096	2,298	2,192
Amortizations	706	608	1,412	1,217
Net periodic benefit cost	$ 1,913	$ 1,789	3,826	$ 3,578
Employer contribution			3,465
Expected future employer contribution			$ 2,400