Available-For-Sale And Held-To-Maturity Securities (Narrative) (Details)		12 Months Ended
		Dec. 31, 2015 USD ($) security	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Proceeds from sale of available-for-sale securities		$ 641,600,000	$ 300,300,000	$ 197,500,000
Net realized gains resulting from sale of available-for-sale securities		3,200,000	3,700,000	2,000,000
Unrealized gains (losses) recorded in accumulated other comprehensive income	[1],[2]	1,389,000	1,838,000	$ (48,528,000)
Financial instruments pledged as collateral		1,400,000,000	1,200,000,000
Trading securities pledged		$ 1,100,000,000
Number of available for sale securities whose amortized costs exceeded their fair values | security		117
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 13,298,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		5,843,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 1,332,902,000
Percentage of available-for-sale portfolio		81.80%
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security		50
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss		$ 7,655,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		3,497,000
Credit-related OTTI		0	0
Gross unrealized losses related to all other securities	[3]	13,298,000	$ 14,172,000
OTTI on all other securities		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		$ 21,000,000

[1] Amounts are net of reclassifications to earnings of realized gains of $2.1 million, $2.3 million, and $1.2 million for the years ended December 31, 2015, 2014, and 2013, respectively

[2] Net of taxes of $0.7 million, $2.1 million, and $24.9 million for the years ended December 31, 2015, 2014, and 2013, respectively

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