Financings - Borrowings under Repurchase Agreements-Maturity dates (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Certain characteristics of the Company's repurchase agreements
Repurchase Agreement Borrowings	$ 1,553,781	$ 2,824,877
1 to 29 days
Certain characteristics of the Company's repurchase agreements
Repurchase Agreement Borrowings	695,385	1,480,286
30 to 59 days
Certain characteristics of the Company's repurchase agreements
Repurchase Agreement Borrowings	244,810	552,786
60 to 89 days
Certain characteristics of the Company's repurchase agreements
Repurchase Agreement Borrowings	37,699	255,814
Greater than or equal to 90 days
Certain characteristics of the Company's repurchase agreements
Repurchase Agreement Borrowings	$ 575,887	$ 535,991