Income Taxes - Federal Statutory Corporate Tax Rate Reconciles to Our Effective Income Tax Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Computed expected tax	$ 137.7	$ 135.9	$ 102.0
State income taxes, net of federal tax benefit	7.6	4.8	12.5
Foreign earnings taxed at lower rates	(22.3)	(22.4)	(22.6)
U.S. tax on foreign earnings	72.3	10.7	(0.5)
Foreign tax credits	(12.1)	(30.3)	(5.3)
Unremitted foreign earnings	0.0	9.4	86.0
Reorganization and divestitures	75.9	0.0	67.9
Net change in valuation allowance	(2.0)	(47.8)	47.8
Net change in unrecognized tax benefits	33.4	16.0	75.3
U.S.Tax Reform	41.1	0.0	0.0
Deferred tax adjustments	14.1	47.1	(75.6)
Other	(15.2)	(9.0)	17.1
Total income tax provision	$ 330.5	$ 95.6	$ 132.6
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Computed expected tax, percentage	35.00%	35.00%	35.00%
State income taxes, net of federal tax benefit, percentage	1.90%	1.20%	4.30%
Foreign earnings taxed at lower rates, percentage	(5.70%)	(5.80%)	(7.80%)
U.S. tax on foreign earnings, percentage	18.40%	2.80%	(0.20%)
Foreign tax credits, percentage	(3.10%)	(7.80%)	(1.80%)
Unremitted foreign earnings, percentage	(0.00%)	2.40%	29.50%
Reorganization and divestitures	19.30%	0.00%	23.30%
Net change in valuation allowance	(0.50%)	(12.30%)	16.40%
Net change in unrecognized tax benefits	8.50%	4.10%	25.80%
U.S.Tax Reform	10.40%	0.00%	0.00%
Deferred tax adjustments	3.60%	12.10%	(25.90%)
Other	(3.80%)	(2.30%)	5.90%
Income tax expense and rate	84.00%	24.60%	45.50%