Available-For-Sale And Held-To-Maturity Securities (Narrative) (Details) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017 USD ($) security	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) security	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Proceeds from sale of available-for-sale securities		$ 87,300	$ 0	$ 87,300	$ 0
Net realized gains resulting from sale of available-for-sale securities		400		400
Unrealized gains (losses) recorded in accumulated other comprehensive loss	[1],[2]	3,770	11,449	7,547	10,421
Financial instruments pledged as collateral		1,900,000		1,900,000		$ 2,000,000
Trading securities pledged		$ 1,900,000		$ 1,900,000		1,700,000
Number of available for sale securities whose amortized costs exceeded their fair values | security		124		124
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses				$ 12,913
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses				4,965
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 832,228		$ 832,228
Percentage of available-for-sale portfolio		24.10%		24.10%
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security		45		45
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss				$ 16,537
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss				1,768
Credit-related OTTI		$ 0	$ 0	0	$ 0
Gross unrealized losses related to investment portfolio	[3]	12,913		12,913		$ 20,411
Available-for-sale and Held-to-maturity Securities [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Gross unrealized losses related to investment portfolio		$ 29,500		$ 29,500

[1] Net of tax expense of $3.7 million and $2.3 million for the three months ended June 30, 2017 and 2016, respectively. Net of tax expense of $8.5 million and tax benefit of $2.5 million for the six months ended June 30, 2017 and 2016, respectively.

[2] There were no reclassifications to earnings during the three and six months ended June 30, 2017 and 2016, respectively.

[3] Unrealized gains/(losses) related to available-for-sale securities are reported in accumulated other comprehensive loss.