Fair Value, Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair value assets measured on recurring basis unobservable input reconciliation calculation [Roll Forward]
Beginning of period balance	$ 25,218	$ 16,793
Total gains or losses (realized) included in income	406	1,846
Purchases	81	5,540
Settlements	(9,123)	(8,791)
Transfers into Level 3	144	10,202
Transfers out of Level 3	(16,726)	(372)
End of period balance	$ 0	$ 25,218