Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 1,431	$ 2,322
Charged to cost and expense	(51)	(343)
Charged to other accounts		(248)
Deductions	635	300
Balance at end of year	745	1,431
Valuation allowance on deferred taxes
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	151,273	142,957
Charged to cost and expense	4,718	8,316
Charged to other accounts	85
Balance at end of year	$ 156,076	$ 151,273