Income Taxes Liability for Uncertain Tax Positions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance at beginning of year	$ 7,125,000	$ 4,197,000	$ 4,324,000
Increase for tax positions related to prior years	246,000	3,970,000	0
Decrease for tax positions related to prior years	0	(1,169,000)	0
Decrease for expiration of statute of limitations	(3,271,000)	0	0
Increase for effects of foreign exchange rates	0	127,000
Decrease for effects of foreign exchange rates			(127,000)
Balance at end of year	$ 4,100,000	$ 7,125,000	$ 4,197,000