Securities In An Unrealized Loss Position Securities In An Unrealized Loss Position (Narrative) (Details) $ in Thousands	Sep. 30, 2016 USD ($) shares	Dec. 31, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	$ 2,556,639	$ 4,170,376
Gross Unrealized Losses	45,198	113,948
Available For Sale Equity Securities Gross Unrealized Gains	6,788	8,216
Loans and Leases Receivable, Other, Allowance	$ 3,000	2,000
Noninvestment Grade Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities | shares	3
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	$ 70,980	22,320
Gross Unrealized Losses	9,028	3,353
Available For Sale Equity Securities Gross Unrealized Gains	6,573	8,216
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	26,228	26,470
Gross Unrealized Losses	2,441	19,189
Available For Sale Equity Securities Gross Unrealized Gains	215	$ 0
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Equity Securities Gross Unrealized Gains	$ 2,000