Consolidated Statement of Member's Equity Consolidated Statement of Member's Equity - USD ($) $ in Thousands	Total	Member's Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period at Dec. 31, 2016		$ 3,678,499	$ 2,462,760	$ 10
Cash contributions from parent	$ 410,000	410,000
Net income	55,728		55,728
Cash distributions to parent	(430,000)		(430,000)
Non-cash distribution to parent			(240,000)
Non-cash distribution of investments in subsidiaries			0	0
Equity interest in unrealized gain (loss) on interest rate hedge	327			327
Balance at end of period at Dec. 31, 2017	5,937,324	4,088,499	1,848,488	337
Cash contributions from parent	340,000	340,000
Net income	741,079		741,079
Cash distributions to parent	(490,000)		(490,000)
Non-cash distribution to parent			0
Non-cash distribution of investments in subsidiaries			0	0
Equity interest in unrealized gain (loss) on interest rate hedge	197			197
Balance at end of period at Dec. 31, 2018	6,528,600	4,428,499	2,099,567	534
Cash contributions from parent	0	0
Net income	963,296		963,296
Cash distributions to parent	(824,000)		(824,000)
Non-cash distribution to parent			(25,000)
Non-cash distribution of investments in subsidiaries			(36,579)	107
Equity interest in unrealized gain (loss) on interest rate hedge	(641)			(641)
Balance at end of period at Dec. 31, 2019	$ 6,605,783	$ 4,428,499	$ 2,177,284	$ 0