Available-For-Sale And Held-To-Maturity Securities (Narrative) (Details) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016 USD ($) security	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) security	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Proceeds from sale of available-for-sale securities		$ 0	$ 552,600	$ 0	$ 552,600
Net realized gains resulting from sale of available-for-sale securities			3,100		3,100
Unrealized gains (losses) recorded in accumulated other comprehensive loss	[1],[2]	11,449	(3,349)	10,421	3,597
Financial instruments pledged as collateral		2,600,000		2,600,000		$ 1,400,000
Trading securities pledged		$ 1,500,000		$ 1,500,000		1,100,000
Number of available for sale securities whose amortized costs exceeded their fair values | security		64		64
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses				$ 10,251
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses				3,612
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 804,683		$ 804,683
Percentage of available-for-sale portfolio		32.60%		32.60%
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security		19		19
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss				$ 2,269
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss				1,195
Credit-related OTTI		$ 0	$ 0	0	$ 0
Gross unrealized losses related to investment portfolio	[3]	10,251		10,251		$ 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		$ 12,500		$ 12,500

[1] Net of tax expense of $2.3 million $2.6 million for the three months ended June 30, 2016 and 2015, respectively. Net of tax benefit of $2.5 million and tax expense of $4.8 million for the six months ended June 30, 2016 and 2015, respectively.

[2] There were no reclassifications to earnings during the three and six months ended June 30, 2016. Amounts are net of reclassifications to earnings of realized gains of $1.9 million and $1.9 million for the three and six months ended June 30, 2015, respectively.

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