Capital Stock, Accumulated Other Comprehensive Loss and Equity - Additional Information (Detail)	3 Months Ended												12 Months Ended			96 Months Ended
	Dec. 31, 2018 USD ($) vote $ / shares shares	Sep. 29, 2018 $ / shares	Jun. 30, 2018 $ / shares	Mar. 31, 2018 $ / shares	Dec. 31, 2017 $ / shares shares	Sep. 30, 2017 $ / shares	Jul. 01, 2017 $ / shares	Apr. 01, 2017 $ / shares	Dec. 31, 2016 $ / shares	Oct. 01, 2016 $ / shares	Jul. 02, 2016 $ / shares	Apr. 02, 2016 $ / shares	Dec. 31, 2018 USD ($) vote $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2018 USD ($) vote $ / shares shares
Equity [Abstract]
Common stock, shares authorized (in shares) | shares	300,000,000				300,000,000								300,000,000	300,000,000		300,000,000
Common stock holders voting right, vote per outstanding share | vote	1												1			1
Common stock, aggregate authorized repurchase amount	$ 5,000,000,000.0												$ 5,000,000,000.0			$ 5,000,000,000.0
Cash paid for Repurchases													$ 704,900,000	$ 450,500,000	$ 658,800,000	$ 4,200,000,000
Repurchases of shares of common stock, average price (in dollars per share) | $ / shares													$ 163.69	$ 150.77	$ 113.26	$ 87.20
Remaining repurchase authorization	$ 799,800,000												$ 799,800,000			$ 799,800,000
Retirement of shares held in treasury (in shares) | shares													8,000,000	8,000,000
Equity, Class of Treasury Stock [Line Items]
Increase (reduction) for retirement of shares held in treasury														$ 0
Cash dividends declared (in dollars per share) | $ / shares	$ 0.7	$ 0.7	$ 0.7	$ 0.7	$ 0.50	$ 0.50	$ 0.50	$ 0.5	$ 0.3	$ 0.3	$ 0.3	$ 0.3
Dividends declared to Lear Corporation stockholders													$ 185,800,000	140,300,000	$ 89,100,000
Dividends paid to Lear Corporation stockholders													186,300,000	137,700,000	88,800,000
Pretax income (loss) related to intercompany transactions for which settlement is not planned or anticipated in the foreseeable future													$ (1,200,000)	900,000	(200,000)
Purchase of remaining noncontrolling interest															32,600,000
Percentage ownership of affiliate after transaction													100.00%
Common stock
Equity, Class of Treasury Stock [Line Items]
Increase (reduction) for retirement of shares held in treasury													$ 100,000	100,000
Additional paid-in capital
Equity, Class of Treasury Stock [Line Items]
Increase (reduction) for retirement of shares held in treasury													155,900,000	155,900,000
Retained earnings
Equity, Class of Treasury Stock [Line Items]
Increase (reduction) for retirement of shares held in treasury													1,014,200,000	735,500,000
Dividends declared to Lear Corporation stockholders													185,800,000	140,300,000	$ 89,100,000
Treasury stock
Equity, Class of Treasury Stock [Line Items]
Increase (reduction) for retirement of shares held in treasury													$ (1,170,200,000)	$ (891,500,000)