Accumulated Other Comprehensive Income - Changes in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Changes in AOCI by component
Beginning balance	$ 55,981	$ 32,627	$ 36,138	$ 29,729
OCI before reclassifications	9,309	7,543	29,217	10,258
Amounts reclassified from AOCI	(19)	78	(84)	261
Net period OCI	9,290	7,621	29,133	10,519
Ending balance	65,271	40,248	65,271	40,248
Effective Portion of Cumulative Loss on Cash Flow Hedges
Changes in AOCI by component
Beginning balance	52	(386)	(26)	(65)
OCI before reclassifications	(3)	107	45	(397)
Amounts reclassified from AOCI	(19)	78	11	261
Net period OCI	(22)	185	56	(136)
Ending balance	30	(201)	30	(201)
Cumulative Unrealized Gain (Loss) on Available-for-Sale Securities
Changes in AOCI by component
Beginning balance	51,682	39,858	44,929	37,307
OCI before reclassifications	3,975	6,105	10,823	8,656
Amounts reclassified from AOCI			(95)
Net period OCI	3,975	6,105	10,728	8,656
Ending balance	55,657	45,963	55,657	45,963
Foreign Currency Translation
Changes in AOCI by component
Beginning balance	4,247	(6,845)	(8,765)	(7,513)
OCI before reclassifications	5,337	1,331	18,349	1,999
Net period OCI	5,337	1,331	18,349	1,999
Ending balance	$ 9,584	$ (5,514)	$ 9,584	$ (5,514)

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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