Carrying Value of Repurchase Agreements (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	$ 580,335,000	$ 569,824,000
Overnight and Continuous
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	580,335,000	569,824,000
Residential mortgage-backed securities
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	328,722,000	312,015,000
Residential mortgage-backed securities | Overnight and Continuous
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	328,722,000	312,015,000
Commercial mortgage-backed securities
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	251,613,000	257,809,000
Commercial mortgage-backed securities | Overnight and Continuous
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	$ 251,613,000	$ 257,809,000