Unfunded Loan Commitments (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jan. 01, 2020	Dec. 31, 2018
Credit Loss [Abstract]
Contractual obligation	$ 1,000,000			$ 1,000,000
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,673,324	$ 441,912	$ 358,325	441,912	$ 341,121	$ 341,121
Less: provisions for credit losses	351,887		93,375	413,145	157,165
Transfer of allowance for funded loans	(46,505)		(74,627)	(117,454)	(129,689)
Ending Balance	1,929,323	1,673,324	383,997	1,929,323	383,997	441,912
Cumulative Effect, Period Of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Day 1 adjustment for the adoption of CECL							$ 1,143,053
Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	29,707		295
Less: provisions for credit losses	98,741		768
Transfer of allowance for funded loans	(42,490)		(308)
Ending Balance	85,958	29,707	755	85,958	755
Unfunded Commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	449,807	1,910,603	518,248	1,910,603	2,010,744	2,010,744
Less: provisions for credit losses	1,165,224		1,348,938	2,000,170	1,982,240
Transfer of allowance for funded loans	(495,989)		(531,431)	(2,791,731)	(2,657,229)
Ending Balance	1,119,042	449,807	1,335,755	1,119,042	1,335,755	1,910,603
Unfunded Commitments | Cumulative Effect, Period Of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Day 1 adjustment for the adoption of CECL						0		$ 0
Unfunded Commitments | Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		$ 2,481		2,481	2,165	2,165
Less: provisions for credit losses				146,804	2,134
Transfer of allowance for funded loans				(179,085)	(3,544)
Ending Balance	$ 85,958		$ 755	$ 85,958	$ 755	2,481
Unfunded Commitments | Consumer Portfolio Segment | Cumulative Effect, Period Of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Day 1 adjustment for the adoption of CECL						$ 115,758		$ 0