Fair Value, Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 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 or losses (realized or unrealized) included in income	443	1,846
Purchases	16,857	5,540
Settlements	(12,847)	(8,791)
Transfers into Level 3	148	10,202
Transfers out of Level 3	(609)	(372)
End of period balance	$ 29,210	$ 25,218