Acquisitions - Additional Information (Detail) € in Millions										3 Months Ended						6 Months Ended		12 Months Ended
	Mar. 10, 2016 USD ($)	Jun. 10, 2015 USD ($)	Jun. 01, 2015 USD ($)	Jun. 01, 2015 EUR (€)	Apr. 08, 2015 USD ($)	Feb. 26, 2015 USD ($)	Feb. 01, 2015 USD ($)	Feb. 01, 2015 EUR (€)	Dec. 30, 2014 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 EUR (€)	Mar. 31, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2015 EUR (€)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2016 USD ($)	Feb. 01, 2015 EUR (€)
Business Acquisition [Line Items]
Assumed debt paid off at closing																$ 91,193,000	$ 26,259,000
TowerSec Ltd. [Member]
Business Acquisition [Line Items]
Business acquisition date																Mar. 10, 2016
Purchase consideration, total	$ 45,000,000
Cash paid to acquire entity	37,900,000
Holdback Amounts in escrow	2,300,000
Deferred consideration amount	$ 3,000,000
Number of years expected to occur certain days	18 months
Approximately third-party debt assumed	$ 2,600,000
Increase (decrease) to purchase price																		$ 100,000
Preliminary valuation of contingent consideration	27,700,000
Acquired intangible assets	4,600,000
Goodwill amount deductible for tax purposes	0
Acquisition costs incurred													$ 600,000
TowerSec Ltd. [Member] | Internally Developed Software
Business Acquisition [Line Items]
Acquired intangible assets	$ 4,600,000
Approximate useful life	6 years
TowerSec Ltd. [Member] | Maximum [Member]
Business Acquisition [Line Items]
Acquisition earn-out contingent payable	$ 30,000,000
Southern Vision Systems Inc [Member]
Business Acquisition [Line Items]
Business acquisition date																Jun. 10, 2015
Purchase consideration, total		$ 20,000,000
Cash paid to acquire entity		19,500,000
Holdback Amounts in escrow		2,400,000
Increase (decrease) to purchase price														$ 100,000
Preliminary valuation of contingent consideration		$ 3,000,000
Escrow released to sellers										$ 2,400,000						$ 2,400,000
Acquisition earn-out contingent payable										10,000,000						$ 10,000,000
Payment towards contingent consideration liability											$ 2,100,000
Bang & Olufsen Automotive Assets [Member]
Business Acquisition [Line Items]
Business acquisition date																Jun. 01, 2015
Purchase consideration, total			$ 165,700,000	€ 150.8
Holdback Amounts in escrow | €				€ 12.5
Increase (decrease) to purchase price														$ 500,000	€ 0.5
Escrow released to sellers | €												€ 12.5
Symphony Teleca Corporation [Member]
Business Acquisition [Line Items]
Business acquisition date																Apr. 08, 2015
Purchase consideration, total					$ 720,800,000
Cash paid to acquire entity					299,700,000
Holdback Amounts in escrow																		42,000,000
Approximately third-party debt assumed					115,600,000
Estimated purchase price paid at closing					491,500,000
Number of shares of common stock to acquire entity					191,800,000
Assumed debt paid off at closing					115,600,000
Acquired of cash					61,900,000
Estimated adjustments to purchase price					0
Business combination additional payments, purchase price																		231,100,000
Business combination additional payments, earn out																		23,300,000
Final base price adjustment																		0
Symphony Teleca Corporation [Member] | Restricted Cash | Non Controlling Interest [Member]
Business Acquisition [Line Items]
Cash paid to acquire entity					$ 14,800,000
Symphony Teleca Corporation [Member] | Escrow One [Member]
Business Acquisition [Line Items]
Holdback Amounts in escrow placed other																		31,200,000
Symphony Teleca Corporation [Member] | Escrow Two [Member]
Business Acquisition [Line Items]
Holdback Amounts in escrow placed other																		$ 21,000,000
Red Bend Ltd. [Member]
Business Acquisition [Line Items]
Business acquisition date																Feb. 26, 2015
Cash paid to acquire entity						$ 71,000,000
Holdback Amounts in escrow						16,000,000
Preliminary valuation of contingent consideration						20,900,000
Escrow released to sellers											15,400,000
Acquisition earn-out contingent payable										$ 30,000,000						$ 30,000,000
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
S1nn GmbH & Co. KG [Member]
Business Acquisition [Line Items]
Business acquisition date																Feb. 01, 2015
Purchase consideration, total							$ 55,400,000	€ 49.0
Holdback Amounts in escrow							$ 4,600,000												€ 4.1
Escrow released to sellers											2,900,000	2.6
Escrow released for specified indemnification matters											1,700,000	€ 1.5
IPSG/VFX [Member] | Harman International Industries Pty Ltd [Member]
Business Acquisition [Line Items]
Business acquisition date																Dec. 30, 2014
Acquisition earn-out contingent payable									$ 0
Escrow released to sellers											$ 700,000
Purchase price									$ 5,000,000
Holdback percentage of contingent payable									15.00%
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