Income Taxes Reconciliation of the change in unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the change in unrecognized tax benefits [Roll Forward]
Unrecognized Tax Benefits, beginning of period	$ 21,502	$ 38,992	$ 32,911
Increases related to tax positions taken during a prior period	20,555	224	5,763
Decreases related to tax positions taken during a prior period	(9,665)	(13,218)	0
Increases related to tax positions taken during the current period	18,895	114	318
Decreases related to settlements with taxing authorities	0	(707)	0
Reductions as a result of a lapse of the statute of limitations	(2,683)	(3,903)	0
Unrecognized Tax Benefits, end of period	$ 48,604	$ 21,502	$ 38,992