Income Taxes Unrecognized tax benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Abstract]
(Reductions) additions based on tax positions related to current year	$ (206)	$ (2,280)
(Reductions) additions based on tax positions related to current year			$ 773
Additions for tax positions of prior years	735	6,688	8,396
Reductions for tax positions of prior years	(488)	(368)	(2,246)
Settlements	(996)	(444)	(364)
Unrecognized tax benefit balance	36,364	$ 37,319	$ 33,723	$ 27,164
Tax benefits, if recognized, affect annual effective tax rate	6,200
Unrecognized tax benefits, potential reduction	19,700
Accrued for payment of interest related to unrecognized tax benefits	3,400
Interest expense related to unrecognized tax benefits	$ 80