Finite-Lived Intangible Assets and Liabilities and Goodwill - Schedule of Major Components of the Finite Lived Intangible Assets and Liabilities (Details) - USD ($)
$ in Thousands |
6 Months Ended |
12 Months Ended |
Jun. 30, 2018 |
Dec. 31, 2017 |
| Intangible assets |
|
|
| Gross |
$ 251,271
|
$ 155,096
|
| Accumulated Amortization |
(24,849)
|
(19,048)
|
| Net |
226,422
|
136,048
|
| Intangible liabilities |
|
|
| Gross |
69,158
|
|
| Accumulated Amortization |
(10,963)
|
|
| Net |
$ 58,195
|
$ 51,194
|
| Power Purchase Agreements [Member] |
|
|
| Intangible assets |
|
|
| Weighted Average Remaining Life |
16 years
|
15 years
|
| Gross |
$ 224,528
|
$ 127,084
|
| Accumulated Amortization |
(23,161)
|
(17,611)
|
| Net |
$ 201,367
|
$ 109,473
|
| Intangible liabilities |
|
|
| Weighted Average Remaining Life |
14 years
|
15 years
|
| Gross |
$ 60,300
|
$ 60,300
|
| Accumulated Amortization |
(10,840)
|
(9,106)
|
| Net |
$ 49,460
|
$ 51,194
|
| Industrial revenue bond tax savings [Member] |
|
|
| Intangible assets |
|
|
| Weighted Average Remaining Life |
24 years
|
24 years
|
| Gross |
$ 12,778
|
$ 12,778
|
| Accumulated Amortization |
(611)
|
(351)
|
| Net |
$ 12,167
|
$ 12,427
|
| Other Intangible Assets [Member] |
|
|
| Intangible assets |
|
|
| Weighted Average Remaining Life |
33 years
|
34 years
|
| Gross |
$ 13,898
|
$ 15,234
|
| Accumulated Amortization |
(1,075)
|
(1,086)
|
| Net |
$ 12,823
|
$ 14,148
|
| Leasehold Interest [Member] |
|
|
| Intangible assets |
|
|
| Weighted Average Remaining Life |
8 years
|
|
| Gross |
$ 67
|
|
| Accumulated Amortization |
(2)
|
|
| Net |
$ 65
|
|
| Intangible liabilities |
|
|
| Weighted Average Remaining Life |
23 years
|
|
| Gross |
$ 8,858
|
|
| Accumulated Amortization |
(123)
|
|
| Net |
$ 8,735
|
|