Acquisitions - Additional Information (Detail) $ / shares in Units, € in Millions									3 Months Ended			12 Months Ended
	Jun. 10, 2015 USD ($)	Jun. 01, 2015 USD ($)	Jun. 01, 2015 EUR (€)	Apr. 08, 2015 USD ($) $ / shares shares	Feb. 26, 2015 USD ($) $ / shares shares	Feb. 01, 2015 USD ($)	Feb. 01, 2015 EUR (€)	Dec. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) shares	Sep. 30, 2015 EUR (€)	Sep. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) shares	Jun. 01, 2015 EUR (€)	Feb. 01, 2015 EUR (€)
Business Acquisition [Line Items]
Goodwill									$ 1,348,761,000			$ 1,287,180,000
Assumed debt paid off at closing									$ 26,082,000		$ 107,500,000
Common stock, shares issued | shares									101,033,756			100,699,641
Measurement Period Adjustments [Member]
Business Acquisition [Line Items]
Cumulative reduction in amortization expense									$ 800,000
Southern Vision Systems Inc [Member]
Business Acquisition [Line Items]
Business acquisition date									Jun. 10, 2015	Jun. 10, 2015
Purchase consideration, total	$ 20,000,000
Cash paid to acquire entity	19,500,000
Holdback Amounts in escrow	$ 2,400,000
Number of years expected to occur certain days	18 months
Increase (decrease) to purchase price									$ 100,000
Preliminary valuation of contingent consideration	$ 0								0
Acquired intangible assets	8,360,000
Acquisition costs incurred												$ 300,000
Goodwill	13,217,000
Acquisition earn-out contingent payable									$ 10,000,000
Southern Vision Systems Inc [Member] | Internally Developed Software [Member]
Business Acquisition [Line Items]
Acquired intangible assets	$ 7,700,000
Approximate useful life	5 years
Southern Vision Systems Inc [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Acquired intangible assets	$ 100,000
Approximate useful life	6 months
Southern Vision Systems Inc [Member] | Distributor Relationships [Member]
Business Acquisition [Line Items]
Acquired intangible assets	$ 600,000
Approximate useful life	2 years
Southern Vision Systems Inc [Member] | Maximum [Member]
Business Acquisition [Line Items]
Acquisition earn-out contingent payable	$ 10,000,000
Bang & Olufsen Automotive Assets [Member]
Business Acquisition [Line Items]
Business acquisition date									Jun. 01, 2015	Jun. 01, 2015
Purchase consideration, total		$ 165,700,000	€ 150.8
Holdback Amounts in escrow | €													€ 12.5
Number of years expected to occur certain days		15 months	15 months
Increase (decrease) to purchase price									$ (500,000)	€ (0.5)
Acquired intangible assets		$ 129,700,000
Acquisition costs incurred												800,000
Goodwill amount deductible for tax purposes		12,800,000
Goodwill		12,769,000
Bang & Olufsen Automotive Assets [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired intangible assets		$ 129,700,000
Approximate useful life		7 years	7 years
Symphony Teleca Corporation [Member]
Business Acquisition [Line Items]
Business acquisition date									Apr. 08, 2015	Apr. 08, 2015
Cash paid to acquire entity				$ 299,700,000
Preliminary valuation of contingent consideration									$ 25,800,000
Acquired intangible assets				202,900,000
Acquisition costs incurred				13,800,000
Goodwill amount deductible for tax purposes				0
Goodwill				602,466,000
Total base purchase price				720,800,000
Estimated purchase price paid at closing				491,500,000
Number of shares of common stock to acquire entity				191,800,000
Approximately third-party debt assumed				115,600,000
Assumed debt paid off at closing				115,600,000
Acquired of cash				61,900,000
Acquisition earn-out contingent payable				24,900,000
Final base price adjustment				$ 0
Common stock, shares issued | shares				1,410,161
Common stock, closing price per share | $ / shares				$ 136.00
Total revaluation adjustment				$ 500,000
Symphony Teleca Corporation [Member] | Accrued Liabilities [Member]
Business Acquisition [Line Items]
Total base purchase price				229,300,000
Symphony Teleca Corporation [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired intangible assets				183,100,000
Symphony Teleca Corporation [Member] | Covenant Not-to-Compete [Member]
Business Acquisition [Line Items]
Acquired intangible assets				$ 1,000,000
Approximate useful life				4 years
Symphony Teleca Corporation [Member] | Technology [Member]
Business Acquisition [Line Items]
Acquired intangible assets				$ 4,200,000
Approximate useful life				3 years
Symphony Teleca Corporation [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Acquired intangible assets				$ 14,600,000
Approximate useful life				9 months
Symphony Teleca Corporation [Member] | Restricted Cash [Member] | Non Controlling Interest [Member]
Business Acquisition [Line Items]
Cash paid to acquire entity				$ 14,800,000
Symphony Teleca Corporation [Member] | Maximum [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Approximate useful life				12 years
Symphony Teleca Corporation [Member] | Minimum [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Approximate useful life				11 years
Red Bend Ltd. [Member]
Business Acquisition [Line Items]
Business acquisition date									Feb. 26, 2015	Feb. 26, 2015
Cash paid to acquire entity					$ 71,000,000
Holdback Amounts in escrow					$ 16,000,000
Number of years expected to occur certain days					18 months
Preliminary valuation of contingent consideration					$ 16,700,000				$ 16,700,000
Acquired intangible assets					50,300,000
Goodwill amount deductible for tax purposes					0
Goodwill					187,131,000
Acquisition earn-out contingent payable									$ 30,000,000
Total revaluation adjustment					4,000,000
Purchase price					195,300,000
Common stock shares consideration, amount					124,300,000
Acquisition, third party debt assumed and paid off					5,600,000
Post-Closing Adjustment					400,000
Consideration Transferred placed in escrow to be used for Post Closing Adjustment					$ 1,000,000
Shares of common stock transferred | shares					897,424
Fair market value of transferred shares of common stock | $ / shares					$ 137.78
Issuance of common shares from treasury stock | shares					839,287
Restricted stock units vested | shares					58,137
Red Bend Ltd. [Member] | Pre-acquisition [Member]
Business Acquisition [Line Items]
Fair value of awards associated with services					$ 600,000
Red Bend Ltd. [Member] | Post-acquisition [Member]
Business Acquisition [Line Items]
Fair value of awards associated with services					1,900,000
Red Bend Ltd. [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired intangible assets					$ 4,000,000
Approximate useful life					5 years
Red Bend Ltd. [Member] | Technology [Member]
Business Acquisition [Line Items]
Acquired intangible assets					$ 46,000,000
Approximate useful life					7 years
Red Bend Ltd. [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Acquired intangible assets					$ 300,000
Approximate useful life					10 months
Red Bend Ltd. [Member] | Maximum [Member]
Business Acquisition [Line Items]
Acquisition earn-out contingent payable					$ 30,000,000
S1nn GmbH & Co. KG [Member]
Business Acquisition [Line Items]
Business acquisition date									Feb. 01, 2015	Feb. 01, 2015
Purchase consideration, total						$ 55,400,000	€ 49.0
Holdback Amounts in escrow						4,600,000								€ 4.1
Acquired intangible assets						25,903,000
Acquisition costs incurred												800,000
Goodwill amount deductible for tax purposes						20,100,000
Goodwill						20,337,000
S1nn GmbH & Co. KG [Member] | Internally Developed Software [Member]
Business Acquisition [Line Items]
Acquired intangible assets						$ 18,300,000
Approximate useful life						7 years	7 years
S1nn GmbH & Co. KG [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired intangible assets						$ 6,900,000
Approximate useful life						9 years	9 years
S1nn GmbH & Co. KG [Member] | Covenant Not-to-Compete [Member]
Business Acquisition [Line Items]
Acquired intangible assets						$ 700,000
Approximate useful life						3 years	3 years
IPSG/VFX [Member]
Business Acquisition [Line Items]
Preliminary valuation of contingent consideration									$ 0
Acquired intangible assets								$ 1,781,000
Goodwill								3,640,000
IPSG/VFX [Member] | Harman International Industries Pty Ltd [Member]
Business Acquisition [Line Items]
Business acquisition date									Dec. 30, 2014	Dec. 30, 2014
Acquisition costs incurred												$ 300,000
Goodwill amount deductible for tax purposes								3,600,000
Goodwill								3,600,000
Acquisition earn-out contingent payable								0
Purchase price								$ 5,000,000
Holdback percentage of contingent payable								15.00%
IPSG/VFX [Member] | Technology [Member] | Harman International Industries Pty Ltd [Member]
Business Acquisition [Line Items]
Acquired intangible assets								$ 1,800,000
Approximate useful life								5 years
IPSG/VFX [Member] | Maximum [Member] | Harman International Industries Pty Ltd [Member]
Business Acquisition [Line Items]
Number of years expected to occur certain days								18 months
Acquisition earn-out contingent payable								$ 8,000,000