Carrying Value of Repurchase Agreements (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	$ 401,243	$ 423,414
Overnight and Continuous
Securities Sold Under Agreements to Repurchase
Repurchase Agreements		420,967
Up to 30 Days
Securities Sold Under Agreements to Repurchase
Repurchase Agreements		2,447
U.S. government sponsored enterprises
Securities Sold Under Agreements to Repurchase
Repurchase Agreements		12,507
U.S. government sponsored enterprises | Overnight and Continuous
Securities Sold Under Agreements to Repurchase
Repurchase Agreements		12,507
U.S. government sponsored enterprises | Up to 30 Days
Securities Sold Under Agreements to Repurchase
Repurchase Agreements		0
Residential mortgage-backed securities
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	401,243	410,907
Residential mortgage-backed securities | Overnight and Continuous
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	400,129	408,460
Residential mortgage-backed securities | Up to 30 Days
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	$ 1,114	$ 2,447