Fair Value, Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Fair Value Assets Measured on Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Beginning of period balance	$ 25,218	$ 16,793
Total gains (realized or unrealized) included in income	316	1,846
Purchases	81	5,540
Settlements	(8,950)	(8,791)
Transfers into Level 3	144	10,202
Transfers out of Level 3	(16,421)	(372)
End of period balance	$ 388	$ 25,218