Retirement Benefits (Schedule of Allocation of Plan Assets, Fair Value Hierarchy) (Details) - Defined Benefit Pension Plan [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 227,722	$ 224,712	$ 208,812
Global Target Return Equity-Bond Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12,495	13,103
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,225	458
Pooled funds: Index linked U.K. government securities fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,913	4,980
Pooled funds: Index linked U.K. long-term government securities fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,817	6,901
Mutual funds: U.S. corporate bond fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	54,699	56,388
Pooled funds: Index linked U.K. corporate bonds fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,121	16,540
Pooled funds: Japanese fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,968	4,987
Pooled funds: International fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,730	1,730
Mutual funds: U.S. equity large cap fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	60,176	54,140
Mutual funds: International equity large cap growth fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47,559	49,513
Pooled funds: Japanese equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,506	2,487
Pooled funds: International equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,214	2,260
Pooled funds: Index linked U.K. equity fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,326	4,940
Pooled funds: Index linked international equity fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,973	6,285
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	165,342	160,332	145,886
UNITED STATES | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	165,342	160,332
UNITED STATES | Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,908	291
UNITED STATES | Fair Value, Inputs, Level 1 [Member] | Mutual funds: U.S. corporate bond fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	54,699	56,388
UNITED STATES | Fair Value, Inputs, Level 1 [Member] | Mutual funds: U.S. equity large cap fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	60,176	54,140
UNITED STATES | Fair Value, Inputs, Level 1 [Member] | Mutual funds: International equity large cap growth fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47,559	49,513
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62,380	64,380	$ 62,926
Foreign Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	317	167
Foreign Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	317	167
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62,063	64,213
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Global Target Return Equity-Bond Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12,495	13,103
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Pooled funds: Index linked U.K. government securities fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,913	4,980
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Pooled funds: Index linked U.K. long-term government securities fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,817	6,901
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Pooled funds: Index linked U.K. corporate bonds fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,121	16,540
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Pooled funds: Japanese fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,968	4,987
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Pooled funds: International fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,730	1,730
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Pooled funds: Japanese equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,506	2,487
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Pooled funds: International equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,214	2,260
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Pooled funds: Index linked U.K. equity fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,326	4,940
Foreign Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Pooled funds: Index linked international equity fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,973	$ 6,285
JAPAN
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,520
UNITED KINGDOM
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50,860
GERMANY
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0