Mortgage Servicing Rights and Mortgage Servicing Liabilities - Activity in MSRs at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Activity in MSRs carried at fair value
Balance at beginning of period			$ 2,807,333
Change in fair value:
Balance at end of period	$ 2,550,602		2,550,602
Mortgage servicing rights
Activity in MSRs carried at fair value
Balance at beginning of period	2,720,335	$ 2,486,157	2,820,612	$ 638,010
Reclassification of mortgage servicing rights previously accounted for under the amortization method								$ 1,482,426
Balance after reclassification					$ 2,720,335	$ 2,820,612	$ 2,486,157	$ 2,120,436
Additions - Mortgage servicing rights resulting from loan sales	246,757	149,000	545,839	448,604
Additions - Purchases	46	163,511	227,445	193,640
Additions	246,803	312,511	773,284	642,244
Change in fair value:
Changes in inputs used in valuation model	(286,880)	64,293	(704,967)	239,538
Other changes in fair value	(124,005)	(76,997)	(332,676)	(216,254)
Total change in fair value	(410,885)	(12,704)	(1,037,643)	23,284
Balance at end of period	2,556,253	2,785,964	2,556,253	2,785,964
Total	$ 2,550,602	$ 2,807,333	$ 2,550,602	$ 2,807,333