Investment Operations Other (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Summary of Investment Holdings [Line Items]
Qualified Affordable Housing Project Investments, Commitment	$ 3,803
Deposit Assets	7,561,900
Available-for-sale Securities Pledged as Collateral	496,800
Other Commitment	50,000
Investment, Non-Income Producing Flag	2,000
Affordable Housing Tax Credit Investments [Member]
Summary of Investment Holdings [Line Items]
Other Commitment, Due in Next Twelve Months	2,898
Other Commitment, Due in Second Year	590
Other Commitment, Due in Third Year	$ 315