Securities in an Unrealized Loss Position (Narrative) (Details) $ in Thousands	Dec. 31, 2015 USD ($) position	Dec. 31, 2014 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Securities in continuous unrealized loss position fair value	$ 4,170,376	$ 2,895,204
Securities in continuous unrealized loss position, aggregate losses accumulated In AOCI	113,948	69,142
Loans and Leases Receivable, Other, Allowance	$ 2,000	3,000
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Securities in unrealized loss positions | position	1
Securities in continuous unrealized loss position fair value	$ 22,320	49,774
Securities in continuous unrealized loss position, aggregate losses accumulated In AOCI	$ 3,353	4,165
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Securities in unrealized loss positions | position	2
Securities in continuous unrealized loss position fair value	$ 26,470	15,929
Securities in continuous unrealized loss position, aggregate losses accumulated In AOCI	$ 19,189	$ 5,453