Fair Values of Financial Instruments - Changes in Level 3 Assets Measured on a Recurring Basis (Details) - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	$ 74	$ 898
Total gains or losses (realized/unrealized):
Included in earnings	0	(298)
Included in other comprehensive income	2	61
Issuances	0	0
Sales	0	(587)
Acquired	60	0
Transfers in and/or out of Level 3	0	0
Balance at the end of the period	$ 136	$ 74