Repurchase Agreements (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($) Security	Dec. 31, 2018 USD ($) Security
Repurchase Agreements [Abstract]
Weighted average of remaining maturities days	54 days	38 days
Repurchase Agreement Characteristics Remaining Maturities [Abstract]
Less than one month, repurchase agreements	$ 623,936	$ 776,666
One to three months, repurchase agreements	1,215,235	821,926
Greater than three months, repurchase agreements	427,670	0
Total repurchase agreements	$ 2,266,841	$ 1,598,592
Repurchase Agreement Characteristics, Weighted Average Rates [Abstract]
Less than one month, weighted average rate	2.50%	2.51%
One to three months, weighted average rate	2.29%	2.56%
Greater than three months, weighted average rate	2.33%	0.00%
Weighted average rate	2.36%	2.54%
Number of overnight or demand securities | Security	0	0