Derivative and Hedging Activities Cumulative Basis Adjustment for Fair Value Hedges (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Balance Sheet Recording of Fair Value Hedge [Line Items]
Trading assets	$ 88,943	$ 69,675
Designated as Hedging Instrument [Member]
Balance Sheet Recording of Fair Value Hedge [Line Items]
Derivative Asset, Amortized Cost Basis	1,100,000
Trading assets	500,000
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	502
adjustment [Member] | Designated as Hedging Instrument [Member]
Balance Sheet Recording of Fair Value Hedge [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	(502)
Carrying Value [Member] | Designated as Hedging Instrument [Member]
Balance Sheet Recording of Fair Value Hedge [Line Items]
Trading assets	$ 499,498