Revenue Disaggregated by Primary Region and Products (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Net sales		$ 2,812.8	$ 2,608.1
Airbag Products
Disaggregation Of Revenue [Line Items]
Net sales		1,443.1	1,354.3	[1]
Seatbelt Products
Disaggregation Of Revenue [Line Items]
Net sales	[1]	797.6	687.1
Restraint Control Systems
Disaggregation Of Revenue [Line Items]
Net sales		245.5	254.7
Active Safety
Disaggregation Of Revenue [Line Items]
Net sales	[1]	213.0	191.5
Brake Systems
Disaggregation Of Revenue [Line Items]
Net sales		113.6	120.5
Passive Safety
Disaggregation Of Revenue [Line Items]
Net sales	[2]	2,240.7	2,041.4
Passive Safety | Airbag Products
Disaggregation Of Revenue [Line Items]
Net sales	[2]	1,443.1	1,354.3	[1]
Passive Safety | Seatbelt Products
Disaggregation Of Revenue [Line Items]
Net sales	[1],[2]	797.6	687.1
Electronics
Disaggregation Of Revenue [Line Items]
Net sales	[2]	572.1	566.7
Electronics | Restraint Control Systems
Disaggregation Of Revenue [Line Items]
Net sales	[2]	245.5	254.7
Electronics | Active Safety
Disaggregation Of Revenue [Line Items]
Net sales	[1],[2]	213.0	191.5
Electronics | Brake Systems
Disaggregation Of Revenue [Line Items]
Net sales	[2]	113.6	120.5
Asia
Disaggregation Of Revenue [Line Items]
Net sales		1,004.1	916.0
Asia | Passive Safety
Disaggregation Of Revenue [Line Items]
Net sales		793.0	708.8
Asia | Electronics
Disaggregation Of Revenue [Line Items]
Net sales		211.1	207.2
China
Disaggregation Of Revenue [Line Items]
Net sales		467.8	423.4
China | Passive Safety
Disaggregation Of Revenue [Line Items]
Net sales		366.7	322.9
China | Electronics
Disaggregation Of Revenue [Line Items]
Net sales		101.1	100.5
Japan
Disaggregation Of Revenue [Line Items]
Net sales		284.4	261.6
Japan | Passive Safety
Disaggregation Of Revenue [Line Items]
Net sales		214.8	200.0
Japan | Electronics
Disaggregation Of Revenue [Line Items]
Net sales		69.6	61.6
Rest of Asia
Disaggregation Of Revenue [Line Items]
Net sales		251.9	231.0
Rest of Asia | Passive Safety
Disaggregation Of Revenue [Line Items]
Net sales		211.5	185.9
Rest of Asia | Electronics
Disaggregation Of Revenue [Line Items]
Net sales		40.4	45.1
Americas
Disaggregation Of Revenue [Line Items]
Net sales		860.8	863.6
Americas | Passive Safety
Disaggregation Of Revenue [Line Items]
Net sales		668.1	648.1
Americas | Electronics
Disaggregation Of Revenue [Line Items]
Net sales		192.7	215.5
Europe
Disaggregation Of Revenue [Line Items]
Net sales		947.9	828.5
Europe | Passive Safety
Disaggregation Of Revenue [Line Items]
Net sales		779.6	684.5
Europe | Electronics
Disaggregation Of Revenue [Line Items]
Net sales		$ 168.3	$ 144.0

[1] Including corporate and other sales.

[2] Excluding intersegment sales.