Valuation and Qualifying Accounts and Reserves (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for uncollectible accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 12,110	$ 10,207	$ 26,389
Charged to Expense	70,824	4,471	4,964
Deductions	(3,435)	2,568	21,146
Balance at End of Year	86,369	12,110	10,207
Valuation allowance for deferred and prepaid tax assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	61,338
Charged to Expense	10,794
Deductions	23,470
Balance at End of Year	48,662	61,338
Valuation allowance for deferred tax assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 61,338	65,377	84,503
Charged to Expense		0	0
Deductions		4,039	19,126
Balance at End of Year		$ 61,338	$ 65,377