Income Taxes - Federal Statutory Corporate Tax Rate Reconciles to Our Effective Income Tax Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Computed expected tax	$ 96.1	$ 137.7	$ 135.9
State income taxes, net of federal tax benefit	8.4	7.6	4.8
Foreign earnings taxed at different rates	8.3	(22.3)	(22.4)
U.S. tax on foreign earnings	13.5	72.3	10.7
Tax credits	(20.7)	(16.8)	(31.5)
Unremitted foreign earnings	0.0	0.0	(9.4)
Reorganization and divestitures	0.0	75.9	0.0
Withholding tax	21.7	7.4	10.1
Net change in valuation allowance	(39.8)	(2.0)	(31.7)
Net change in unrecognized tax benefits	95.0	33.4	16.0
Tax Cuts and Jobs Act	117.6	41.1	0.0
Deferred tax adjustments	0.0	14.1	31.0
Other	7.4	(17.9)	(17.9)
Total income tax provision	$ 307.5	$ 330.5	$ 95.6
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Computed expected tax	21.00%	35.00%	35.00%
State income taxes, net of federal tax benefit	1.80%	1.90%	1.20%
Foreign earnings taxed at different rates	1.80%	(5.70%)	(5.80%)
U.S. tax on foreign earnings	2.90%	18.40%	2.80%
Tax credits	(4.50%)	(4.30%)	(8.10%)
Unremitted foreign earnings	0.00%	0.00%	(2.40%)
Reorganization and divestitures	0.00%	19.30%	0.00%
Withholding tax	4.70%	1.90%	2.60%
Net change in valuation allowance	(8.70%)	(0.50%)	(8.20%)
Net change in unrecognized tax benefits	20.80%	8.50%	4.10%
Tax Cuts and Jobs Act	25.70%	10.50%	0.00%
Deferred tax adjustments	0.00%	3.60%	8.00%
Other	1.70%	(4.60%)	(4.60%)
Income tax expense and rate	67.20%	84.00%	24.60%