Fair Value, Company's Level 3 Assets (Servicing Related Assets) Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2019	Dec. 31, 2018
Servicing Related Assets [Abstract]
Beginning balance	[1]	$ 294,907
Changes in Fair Value due to [Abstract]
Ending balance	[1]	255,845	$ 294,907
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Servicing Related Assets [Abstract]
Beginning balance		294,907
Changes in Fair Value due to [Abstract]
Ending balance		255,845	294,907
MSRs [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Servicing Related Assets [Abstract]
Beginning balance		294,907	122,806
Purchases and other changes [Abstract]
Purchases		71,294	178,192
Other changes	[2]	(1,625)	(2,518)
Purchases and other changes		69,669	175,674
Changes in Fair Value due to [Abstract]
Changes in valuation inputs or assumptions used in valuation model		(68,740)	14,648
Other changes in fair value	[3]	(39,991)	(18,221)
Unrealized gain (loss) included in Net Income		(108,731)	(3,573)
Ending balance		$ 255,845	$ 294,907

[1] Carrying value represents the fair value of the pools (see Note 9).

[2] Represents purchase price adjustments, principally contractual prepayment protection, and changes due to the Company's repurchase of the underlying collateral.

[3] Represents changes due to realization of expected cash flows and estimated MSR runoff.