Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Segment Information
Net sales	$ 792,686	$ 806,961	$ 779,026	$ 827,105	$ 813,111	$ 802,829	$ 757,874	$ 789,227	$ 3,205,778	$ 3,163,041	$ 2,999,733
Income (loss) from operations									102,740	329,765	394,370
Depreciation and amortization									106,557	110,636	102,271
Capital expenditures									105,207	129,220	86,314
Goodwill and intangible asset impairment charges									207,334
Facility restructuring charges							30,200			32,695
Provision as per best estimate					12,000		12,000			12,000
Netherlands
Segment Information
Net sales									116,107	98,673	84,167
U.K.
Segment Information
Net sales									767,173	675,378	641,752
Ireland
Segment Information
Net sales									40,235	36,655	33,341
Reportable Business Segments
Segment Information
Net sales									3,205,778	3,163,041	2,999,733
Income (loss) from operations									199,641	465,933	471,981
Depreciation and amortization									68,803	63,682	67,380
Capital expenditures									58,348	38,137	23,959
Corporate/Manufacturing
Segment Information
Income (loss) from operations									(96,901)	(136,168)	(77,611)
Depreciation and amortization									37,754	46,954	34,891
Capital expenditures									46,859	91,083	62,355
Wholesale segment | Reportable Business Segments
Segment Information
Net sales									1,879,481	1,938,921	1,826,780
Income (loss) from operations									177,069	231,812	241,504
Depreciation and amortization									36,092	36,517	39,692
Capital expenditures									482	971	804
European Retail | Belgium
Segment Information
Number of stores	15								15
European Retail | Holland & Barrett
Segment Information
Number of stores	755								755
European Retail | Holland & Barrett | China
Segment Information
Number of franchised stores	29								29
European Retail | Holland & Barrett | Singapore
Segment Information
Number of franchised stores	28								28
European Retail | Holland & Barrett | United Arab Emirates
Segment Information
Number of franchised stores	11								11
European Retail | Holland & Barrett | Cyprus
Segment Information
Number of franchised stores	9								9
European Retail | Holland & Barrett | Malta
Segment Information
Number of franchised stores	4								4
European Retail | Holland & Barrett | Gibraltar
Segment Information
Number of franchised stores	1								1
European Retail | Holland & Barrett | Iceland
Segment Information
Number of franchised stores	1								1
European Retail | De Tuinen | Netherlands
Segment Information
Number of stores	146								146
Number of franchised stores	6								6
European Retail | GNC (UK) stores | U.K.
Segment Information
Number of stores	53								53
European Retail | Nature's Way | Ireland
Segment Information
Number of stores	47								47
European Retail | Reportable Business Segments
Segment Information
Net sales									850,797	743,861	699,675
Income (loss) from operations									191,207	170,479	157,540
Depreciation and amortization									18,048	14,320	13,988
Capital expenditures									42,315	27,198	22,428
Direct Response / E-Commerce
Segment Information
Goodwill and intangible asset impairment charges									171,590
Direct Response / E-Commerce | Reportable Business Segments
Segment Information
Net sales									250,224	246,731	239,409
Income (loss) from operations									(141,660)	39,104	46,179
Depreciation and amortization									11,319	10,137	10,504
Capital expenditures									1,456	4,411	131
North American Retail
Segment Information
Goodwill and intangible asset impairment charges									35,744
North American Retail | Vitamin World
Segment Information
Number of stores	414								414
North American Retail | Reportable Business Segments
Segment Information
Net sales									225,276	233,528	233,869
Income (loss) from operations									(26,975)	24,538	26,758
Depreciation and amortization									3,344	2,708	3,196
Capital expenditures									$ 14,095	$ 5,557	$ 596