Supplemental Guarantor Information (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014
Current assets:
Cash and cash equivalents	$ 14,841	$ 45,661	$ 22,956	$ 54,472
Accounts receivable, net	490,850	399,732	248,154
Inventories, net	513,750	320,999	361,317
Prepaid expenses and other current assets	164,625	97,928	73,490
Total current assets	1,184,066	864,320	705,917
Intercompany receivable, net	0	0	0
Investments in consolidated subsidiaries	0	0	0
Deferred income taxes, net	0	2,300	14,800
Property and equipment, net	147,994	90,405	85,054
Goodwill	1,160,775	496,415	488,324	$ 466,206
Intangibles, net	472,582	87,055	91,650
Other assets, net	1,430	1,233	3,012
Total Assets	2,966,847	1,539,428	1,373,957
Current liabilities:
Accounts payable	417,994	244,891	202,713
Accrued expenses	152,692	124,794	80,546
Borrowings under revolving lines of credit	0	11,240	3,948
Current portions of long-term debt	12,159	16,320	16,612
Total current liabilities	582,845	397,245	303,819
Intercompany payable, net	0	0	0
Long-term debt, net of current	722,542	170,200	178,241
Borrowings under revolving lines of credit	295,690	0	0
Deferred income taxes, net	102,878	66,500	48,637
Long-term obligations under equipment financing and other, net of current	42,907	22,367	24,779
Total liabilities	1,746,862	656,312	555,476
Total stockholders' equity	1,219,985	883,116	818,481
Total Liabilities and Stockholders' Equity	2,966,847	1,539,428	1,373,957
Parent Company [Member]
Current assets:
Cash and cash equivalents	0	0	0
Accounts receivable, net	0	0	0
Inventories, net	0	0	0
Prepaid expenses and other current assets	16,474	14,013	16,146
Total current assets	16,474	14,013	16,146
Intercompany receivable, net	0	0	0
Investments in consolidated subsidiaries	2,716,780	1,429,665	1,359,194
Deferred income taxes, net	17,403	20,532	14,315
Property and equipment, net	3,740	2,339	2,585
Goodwill	0	0	0
Intangibles, net	0	0	12
Other assets, net	1,233	1,233	1,644
Total Assets	2,755,630	1,467,782	1,393,896
Current liabilities:
Accounts payable	34,045	14,519	17,479
Accrued expenses	10,390	38,744	6,959
Borrowings under revolving lines of credit		0	0
Current portions of long-term debt	4,500	11,250	11,250
Total current liabilities	48,935	64,513	35,688
Intercompany payable, net	764,168	349,908	361,441
Long-term debt, net of current	722,542	170,200	178,241
Borrowings under revolving lines of credit	0
Deferred income taxes, net	0	0	0
Long-term obligations under equipment financing and other, net of current	0	45	45
Total liabilities	1,535,645	584,666	575,415
Total stockholders' equity	1,219,985	883,116	818,481
Total Liabilities and Stockholders' Equity	2,755,630	1,467,782	1,393,896
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	28,831	42,816	25,487
Accounts receivable, net	476,860	365,679	233,912
Inventories, net	483,582	299,107	329,748
Prepaid expenses and other current assets	145,102	78,314	70,729
Total current assets	1,134,375	785,916	659,876
Intercompany receivable, net	802,015	386,892	397,545
Investments in consolidated subsidiaries	0	0	0
Deferred income taxes, net	0	0	0
Property and equipment, net	135,511	79,428	73,998
Goodwill	1,130,818	465,575	457,220
Intangibles, net	468,881	84,915	88,896
Other assets, net	197	0	0
Total Assets	3,671,797	1,802,726	1,677,535
Current liabilities:
Accounts payable	392,032	218,920	178,286
Accrued expenses	137,378	80,738	87,907
Borrowings under revolving lines of credit		0	0
Current portions of long-term debt	7,659	5,070	5,362
Total current liabilities	537,069	304,728	271,555
Intercompany payable, net	0	0	0
Long-term debt, net of current	0	0	0
Borrowings under revolving lines of credit	295,690
Deferred income taxes, net	119,855	86,860	63,264
Long-term obligations under equipment financing and other, net of current	42,860	22,256	24,665
Total liabilities	995,474	413,844	359,484
Total stockholders' equity	2,676,323	1,388,882	1,318,051
Total Liabilities and Stockholders' Equity	3,671,797	1,802,726	1,677,535
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	4,689	7,051	5,962
Accounts receivable, net	15,130	34,693	15,010
Inventories, net	30,168	21,892	31,569
Prepaid expenses and other current assets	3,049	5,601	2,761
Total current assets	53,036	69,237	55,302
Intercompany receivable, net	0	0	0
Investments in consolidated subsidiaries	0	0	0
Deferred income taxes, net	0	0	310
Property and equipment, net	8,743	8,638	8,471
Goodwill	29,957	30,840	31,104
Intangibles, net	3,701	2,140	2,742
Other assets, net	0	0	1,368
Total Assets	95,437	110,855	99,297
Current liabilities:
Accounts payable	11,736	16,298	16,208
Accrued expenses	4,924	5,312	1,825
Borrowings under revolving lines of credit		11,240	3,948
Current portions of long-term debt	0	0	0
Total current liabilities	16,660	32,850	21,981
Intercompany payable, net	37,847	36,984	36,104
Long-term debt, net of current	0	0	0
Borrowings under revolving lines of credit	0
Deferred income taxes, net	426	172	0
Long-term obligations under equipment financing and other, net of current	47	66	69
Total liabilities	54,980	70,072	58,154
Total stockholders' equity	40,457	40,783	41,143
Total Liabilities and Stockholders' Equity	95,437	110,855	99,297
Eliminations and Other [Member]
Current assets:
Cash and cash equivalents	(18,679)	(4,206)	(8,493)
Accounts receivable, net	(1,140)	(640)	(768)
Inventories, net	0	0	0
Prepaid expenses and other current assets	0	0	(16,146)
Total current assets	(19,819)	(4,846)	(25,407)
Intercompany receivable, net	(802,015)	(386,892)	(397,545)
Investments in consolidated subsidiaries	(2,716,780)	(1,429,665)	(1,359,194)
Deferred income taxes, net	(17,403)	(20,532)	(14,625)
Property and equipment, net	0	0	0
Goodwill	0	0	0
Intangibles, net	0	0	0
Other assets, net	0	0	0
Total Assets	(3,556,017)	(1,841,935)	(1,796,771)
Current liabilities:
Accounts payable	(19,819)	(4,846)	(9,260)
Accrued expenses	0	0	(16,145)
Borrowings under revolving lines of credit		0	0
Current portions of long-term debt	0	0	0
Total current liabilities	(19,819)	(4,846)	(25,405)
Intercompany payable, net	(802,015)	(386,892)	(397,545)
Long-term debt, net of current	0	0	0
Borrowings under revolving lines of credit	0
Deferred income taxes, net	(17,403)	(20,532)	(14,627)
Long-term obligations under equipment financing and other, net of current	0	0	0
Total liabilities	(839,237)	(412,270)	(437,577)
Total stockholders' equity	(2,716,780)	(1,429,665)	(1,359,194)
Total Liabilities and Stockholders' Equity	$ (3,556,017)	$ (1,841,935)	$ (1,796,771)