Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Provision For Doubtful Accounts	$ 19,519	$ 14,053	$ 16,369
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Balance, Beginning Balance	16,500	14,300	14,200
Provision For Doubtful Accounts	19,500	14,100	16,400
Write-Offs	(18,300)	(11,900)	(16,300)
Valuation Allowances and Reserves, Balance, Ending Balance	17,700	16,500	14,300
Allowance for Doubtful Accounts - Discontinued Operations [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Provision For Doubtful Accounts			100
Estimated Revenue Adjustments [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Balance, Beginning Balance	4,000	3,100	3,900
Provision for Estimated Revenue Adjustments	7,900	6,100	5,100
Write-Offs	(7,800)	(5,200)	(5,900)
Valuation Allowances and Reserves, Balance, Ending Balance	$ 4,100	$ 4,000	3,100
Estimated Revenue Adjustments, Discontinued Operations [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Provision for Estimated Revenue Adjustments			$ 100