Segment and Geographic Information - Geographic Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	$ 248.4	$ 242.7	$ 233.5	$ 245.5	$ 232.4	$ 263.0	$ 258.8	$ 255.1	$ 970.1	$ 1,009.3	$ 942.5
Long-Lived Assets	296.5				301.1				296.5	301.1	351.9
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									349.4	361.3	330.3
Long-Lived Assets	138.3				139.9				138.3	139.9	153.9
Taiwan
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									230.8	236.3	228.0
Long-Lived Assets	36.8				39.7				36.8	39.7	43.7
South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									217.2	220.3	184.3
Long-Lived Assets	112.2				105.0				112.2	105.0	122.0
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									53.8	70.9	76.9
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									57.8	69.2	70.3
Long-Lived Assets	0.2				0.1				0.2	0.1	0.9
Asia, excluding China, Taiwan, and South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									61.1	51.3	52.7
Long-Lived Assets	$ 9.0				$ 16.4				$ 9.0	$ 16.4	$ 31.4