Isle Acquisition and Preliminary Purchase Price Accounting - Schedule of Purchase Consideration Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	May 01, 2017	Jun. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Shares of ERI common stock issued for Isle common stock, shares		76,625,525	47,105,744
Isle Acquisition
Business Acquisition [Line Items]
Cash paid for outstanding Isle common stock	$ 552,050
Shares of ERI common stock issued for Isle common stock, shares	28,468,182
Shares of ERI common stock issued for Isle common stock, per share	$ 19.12
Shares of ERI common stock issued for Isle common stock	$ 544,312
Cash paid by ERI to retire Isle's long-term debt	828,000
Shares of ERI common stock for Isle equity awards	10,383
Purchase consideration	$ 1,934,745