Schedule II -- Valuation and Qualifying Accounts (Consolidated) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts & Discounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		$ 7,832	$ 7,066	$ 5,586
Charged to expense or other accounts		1,291	1,118	2,719
Deductions	[1]	(72)	(352)	(1,239)
Balance at end of period		9,051	7,832	7,066
Valuation Allowance for Deferred Tax Asset
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		13,773	11,184	66,486
Charged to expense or other accounts		5,303	2,589	6,093
Deductions	[2]	0	0	(61,395)
Balance at end of period		$ 19,076	$ 13,773	$ 11,184

[1] Uncollectible accounts written off, net of recoveries.

[2] The net decrease in valuation allowance is primarily a result of net changes in cumulative book/tax timing differences and, with respect to activity for the year ended December 31, 2015, changes in judgment regarding the realizability of U.S. deferred tax assets.