Borrowings Summary of Repurchase Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	$ 473,650	$ 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
Mortgage-backed securities
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	473,650	410,907
Mortgage-backed securities | Overnight and Continuous
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	473,007	408,460
Mortgage-backed securities | Up to 30 Days
Securities Sold Under Agreements to Repurchase
Repurchase Agreements	$ 643	$ 2,447