Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Less than 12 months, Fair Value	$ 4,036,153	$ 4,352,838
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	50,837	31,844
12 months or longer, Fair Value	444,252	767,349
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	10,105	20,776
Total, Fair Value	4,480,405	5,120,187
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	60,942	52,620
US Treasury and Government [Member]
Investment [Line Items]
Less than 12 months, Fair Value	349,538	491,998
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,823	3,098
12 months or longer, Fair Value	32,208	31,012
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3,489	4,723
Total, Fair Value	381,746	523,010
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	6,312	7,821
US Government-sponsored Enterprise Debt Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	190,441	157,830
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,576	1,975
12 months or longer, Fair Value	0	110,250
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	2,571
Total, Fair Value	190,441	268,080
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	1,576	4,546
State and municipal obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	700,779	66,998
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	12,164	544
12 months or longer, Fair Value	15,195	31,120
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	529	1,195
Total, Fair Value	715,974	98,118
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	12,693	1,739
Agency mortgage-backed securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	1,147,416	530,035
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	20,638	2,989
12 months or longer, Fair Value	2,150	291,902
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5	5,617
Total, Fair Value	1,149,566	821,937
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	20,643	8,606
Non-agency mortgage-backed securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	688,131	653,603
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6,373	7,059
12 months or longer, Fair Value	34,946	54,536
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	120	760
Total, Fair Value	723,077	708,139
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	6,493	7,819
Asset-backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	780,209	2,207,922
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5,277	12,492
12 months or longer, Fair Value	358,778	223,311
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5,936	4,615
Total, Fair Value	1,138,987	2,431,233
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	11,213	17,107
Total mortgage and asset-backed securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	2,615,756	3,391,560
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	32,288	22,540
12 months or longer, Fair Value	395,874	569,749
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	6,061	10,992
Total, Fair Value	3,011,630	3,961,309
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	38,349	33,532
Other debt securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	179,639	244,452
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,986	3,687
12 months or longer, Fair Value	975	25,218
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	26	1,295
Total, Fair Value	180,614	269,670
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 2,012	$ 4,982