Available-For-Sale And Held-To-Maturity Securities (Narrative) (Details)		3 Months Ended		9 Months Ended
		Sep. 30, 2015 USD ($) security	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) security	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Proceeds from sale of available-for-sale securities		$ 89,000,000		$ 641,600,000
Net realized gains resulting from sale of available-for-sale securities		100,000		3,200,000
Unrealized gains (losses) recorded in accumulated other comprehensive income	[1],[2]	(611,000)	$ (3,884,000)	5,261,000	$ 1,683,000
Financial instruments pledged as collateral		908,200,000		908,200,000		$ 1,200,000,000
Trading securities pledged		$ 388,500,000		$ 388,500,000
Number of available for sale securities whose amortized costs exceeded their fair values | security		48		48
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses				$ 6,857,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses				4,618,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 387,347,000		$ 387,347,000
Percentage of available-for-sale portfolio		58.70%		58.70%
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				$ 3,076,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss				3,003,000
Credit-related OTTI		$ 0	$ 0	0	$ 0
Gross unrealized losses related to all other securities	[3]	6,857,000		6,857,000		$ 14,172,000
OTTI on all other securities		0		0
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 all other securities		$ 9,900,000		$ 9,900,000

[1] Amounts are net of reclassifications to earnings of realized gains of $0.2 million and $0.7 million for the three months ended September 30, 2015 and 2014, respectively. Amounts are net of reclassifications to earnings of realized gains of $2.1 million and $1.9 million for the nine months ended September 30, 2015 and 2014, respectively.

[2] Net of tax benefit of $2.4 million and $7.0 million for the three months ended September 30, 2015 and 2014, respectively. Net of taxes of $2.4 million and a tax benefit of $1.6 million for the nine months ended September 30, 2015 and 2014, respectively.

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