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	$ 131,171
Net income (loss)	165,858
Ending balance, shares at Sep. 30, 2020		1,000
Ending balance at Sep. 30, 2020	6,155,666		1,100,983	195,495	4,859,188
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
Net income (loss)					(270,593)
Ending balance, shares at Jun. 30, 2020		1,000
Ending balance at Jun. 30, 2020			1,100,882	143,308	4,739,382
Share-based compensation plans			101
Net increase (decrease) during the period	52,187			52,187
Net income (loss)	119,806				119,806
Ending balance, shares at Sep. 30, 2020		1,000
Ending balance at Sep. 30, 2020	6,155,666		1,100,983	195,495	4,859,188
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	$ (98,804)
Net income (loss)	$ 441,936
Ending balance, shares at Sep. 30, 2021	1,000	1,000
Ending balance at Sep. 30, 2021	$ 6,757,778		1,101,425	169,214	5,487,139
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
Net income (loss)					465,807
Ending balance, shares at Jun. 30, 2021		1,000
Ending balance at Jun. 30, 2021			1,101,316	229,835	5,630,453
Share-based compensation plans			109
Net increase (decrease) during the period	(60,621)			(60,621)
Net income (loss)	$ (143,313)				(143,313)
Ending balance, shares at Sep. 30, 2021	1,000	1,000
Ending balance at Sep. 30, 2021	$ 6,757,778		$ 1,101,425	$ 169,214	$ 5,487,139