Available-For-Sale And Held-To-Maturity Securities (Narrative) (Details) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016 USD ($) security	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) security	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Proceeds from sale of available-for-sale securities		$ 0	$ 89,000	$ 0	$ 641,600
Net realized gains resulting from sale of available-for-sale securities			100		3,200
Unrealized gains (losses) recorded in accumulated other comprehensive loss	[1],[2]	4,494	(1,827)	14,915	1,770
Financial instruments pledged as collateral		1,900,000		1,900,000		$ 1,400,000
Trading securities pledged		$ 1,700,000		$ 1,700,000		1,100,000
Number of available for sale securities whose amortized costs exceeded their fair values | security		73		73
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses				$ 7,036
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses				2,150
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 810,543		$ 810,543
Percentage of available-for-sale portfolio		25.80%		25.80%
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security		21		21
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss				$ 1,723
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss				1,266
Credit-related OTTI		$ 0	$ 0	0	$ 0
Gross unrealized losses related to investment portfolio	[3]	7,036		7,036		$ 13,298
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		$ 8,800		$ 8,800

[1] Net of tax expense of $5.8 million and $2.4 million for the three months ended September 30, 2016 and 2015, respectively. Net of tax expense of $3.4 million and tax expense of $2.4 million for the nine months ended September 30, 2016 and 2015, respectively.

[2] There were no reclassifications to earnings during the three and nine months ended September 30, 2016. Amounts are net of reclassifications to earnings of realized gains of $0.2 million and $2.1 million for the three and nine months ended September 30, 2015, respectively.

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