Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Account receivable allowances	$ 6.0	$ 6.0
Accrued compensation and benefits	79.2	119.3
Accumulated depreciation and amortization	1.2	1.3
Stock-based compensation	39.6	54.4
Deferred rent and construction allowance	21.2	30.1
Deferred revenue	41.9	46.2
Foreign net operating loss	13.3	3.7
Settlement Charge		163.2
Legal and professional fees	1.2	4.2
Restructuring	0.2	2.2
Uncertain tax positions	28.6	37.3
Self-insured related reserves	7.5	15.1
Capitalized Cost	4.3
Other	19.0	4.5
Total deferred tax assets	263.2	487.5
Deferred tax liabilities:
Accumulated depreciation and amortization of intangible assets and capitalized software	(408.8)	(189.8)
Foreign earnings to be repatriated		(7.5)
Capital gains	(25.6)	(24.1)
Self-insured related income	(7.5)	(15.1)
Stock based compensation	(3.3)	(2.9)
Unrealized gains on net investment hedges - OCI	0.0	(21.0)
Other	(3.0)	(12.1)
Total deferred tax liabilities	(448.2)	(272.5)
Net deferred tax (liabilities) asset	(185.0)	215.0
Valuation allowance	(12.8)	(3.2)	$ (4.3)	$ (6.9)
Total net deferred tax (liabilities) assets	$ (197.8)	$ 211.8