Income Taxes - Schedule of Reconciliation of Income Tax Expense to Amount Computed at the Federal Statutory Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax at statutory rate	$ 259,884	$ (138,084)	$ 149,296
Federal tax reform	(1,205,140)	0	0
State income taxes	(52,606)	(71,613)	(7,566)
Valuation allowance	10,680	23,808	91,144
Noncontrolling partners’ share of earnings	(122,365)	(112,672)	(82,850)
Regulatory liability/asset	10,488	35,438	(35,438)
Federal tax credits	(34,956)	(4,539)	(7,243)
Other	18,396	4,198	(2,668)
Total income taxes	$ (1,115,619)	$ (263,464)	$ 104,675
Effective tax rate	(150.20%)	66.80%	24.50%