Consolidated Statements Of Changes In Stockholder's Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss), Net Of Deferred Income Taxes [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect Period Of Adoption Adjustment [Member]
Beginning balance at Dec. 31, 2019			$ 1,100,678	$ 64,324	$ 4,692,423
Beginning balance (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2019						$ 907
Beginning balance, shares at Dec. 31, 2019		1,000
Share-based compensation plans			103
Net increase (decrease) during the period				(178,351)
Net income (loss)					316,645
Ending balance, shares at Mar. 31, 2020		1,000
Ending balance at Mar. 31, 2020			1,100,781	(114,027)	5,009,975
Beginning balance at Dec. 31, 2019			1,100,678	64,324	4,692,423
Beginning balance (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2019						907
Beginning balance, shares at Dec. 31, 2019		1,000
Net increase (decrease) during the period	$ 78,984
Net income (loss)	46,052
Ending balance, shares at Jun. 30, 2020		1,000
Ending balance at Jun. 30, 2020	5,983,572		1,100,882	143,308	4,739,382
Beginning balance at Mar. 31, 2020			1,100,781	(114,027)	5,009,975
Beginning balance, shares at Mar. 31, 2020		1,000
Share-based compensation plans			101
Net increase (decrease) during the period	257,335			257,335
Net income (loss)	(270,593)				(270,593)
Ending balance, shares at Jun. 30, 2020		1,000
Ending balance at Jun. 30, 2020	5,983,572		1,100,882	143,308	4,739,382
Beginning balance at Dec. 31, 2020	$ 6,414,313		1,101,092	268,018	5,045,203
Beginning balance (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2020
Beginning balance, shares at Dec. 31, 2020	1,000	1,000
Share-based compensation plans			108
Net increase (decrease) during the period				(104,063)
Net income (loss)					119,443
Ending balance, shares at Mar. 31, 2021		1,000
Ending balance at Mar. 31, 2021			1,101,200	163,955	5,164,646
Beginning balance at Dec. 31, 2020	$ 6,414,313		1,101,092	268,018	5,045,203
Beginning balance (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2020
Beginning balance, shares at Dec. 31, 2020	1,000	1,000
Net increase (decrease) during the period	$ (38,183)
Net income (loss)	$ 585,250
Ending balance, shares at Jun. 30, 2021	1,000	1,000
Ending balance at Jun. 30, 2021	$ 6,961,604		1,101,316	229,835	5,630,453
Beginning balance at Mar. 31, 2021			1,101,200	163,955	5,164,646
Beginning balance, shares at Mar. 31, 2021		1,000
Share-based compensation plans			116
Net increase (decrease) during the period	65,880			65,880
Net income (loss)	$ 465,807				465,807
Ending balance, shares at Jun. 30, 2021	1,000	1,000
Ending balance at Jun. 30, 2021	$ 6,961,604		$ 1,101,316	$ 229,835	$ 5,630,453