Additional Details Related to Certain Balance Sheet Captions (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other current assets:
Prepaid taxes	$ 94.9	$ 47.0
Prepaid expenses	107.6	65.7
Other	47.6	28.1
Total other current assets	250.1	140.8
Other assets:
Investments in joint ventures	99.1	26.3
Deposits for real-estate leases	12.3	10.8
Indemnification assets related to acquisitions	17.0	16.5
Fixed maturity and other open ended mutual funds	22.1	32.7
Other	9.4	25.9
Total other assets	159.9	112.2
Accounts payable and accrued liabilities:
Salaries and benefits	129.6	89.3
Incentive compensation	246.7	151.1
Accrued settlement charge		863.8
Customer credits, advanced payments and advanced billings	22.2	28.4
Self-insurance reserves	8.1	11.1
Dividends	6.2	78.5
Professional service fees	47.1	40.4
Interest accrued on debt	73.9	59.2
Accounts payable	21.8	28.4
Income taxes	79.2	16.8
Restructuring	0.4	6.3
Pension and other retirement employee benefits	5.9	6.1
Accrued royalties	26.4	1.8
Other	82.8	63.1
Total accounts payable and accrued liabilities	750.3	1,444.3
Other liabilities:
Pension and other retirement employee benefits	244.5	264.1
Deferred rent-non-current portion	103.1	98.3
Interest accrued on UTPs	54.7	34.1
Legacy and other tax matters	1.3	1.2
Income Tax Liability - Non Current	232.2	0.0
Other	28.2	27.5
Total other liabilities	$ 664.0	$ 425.2