Investments - Equity Securities (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)
Investments
Investments - equity securities	$ 38,830	$ 38,830
Unrealized gains on investments - equity securities	$ 1,267	729
Reclassification into retained earnings		$ 932	[1]

[1] The reclassification into retained earnings relates to the adoption of Accounting Standards Update (“ASU”) 201601 Financial Instruments - Overall, as amended (“ASU 201601”). The new guidance was effective January 1, 2018, and requires equity investments to be measured at fair value with changes in fair value recognized in results of operations rather than the condensed consolidated statements of comprehensive income. See Note 2. Summary of Significant Accounting Policies.