Investments (Fair Value and Gross Pre-Tax Net Unrealized Unrecognized Loss of Securities By Length of Time) (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014
AFS Fair Value, Less than 12 months		$ 879,619	$ 466,387
AFS Unrealized Losses, Less than 12 months	[1]	(21,084)	(2,408)
AFS Fair Value, 12 months or longer		144,459	442,058
AFS Unrealized Losses, 12 months or longer	[1]	(2,760)	(8,170)
HTM Fair Value, Less than 12 months		0	196
HTM Unrealized Losses, Less than 12 months	[1]	0	(3)
HTM Unrecognized Gains, Less than 12 months	[2]	0	1
HTM Fair Value, 12 months or longer		942	2,235
HTM Unrealized Losses, 12 months or longer	[1]	(157)	(455)
HTM Unrecognized Gains, 12 months or longer	[2]	153	439
Total AFS and HTM Fair Value, Less than 12 months		879,619	466,583
Total AFS and HTM Unrealized Losses, Less than 12 months	[1]	(21,084)	(2,411)
Total AFS and HTM Securities Unrecognized Gains, Less Than 12 Months	[2]	0	1
Total AFS and HTM Fair Value, 12 months or longer		145,401	444,293
Total AFS and HTM Unrealized Losses, 12 months or longer	[1]	(2,917)	(8,625)
Total AFS and HTM Securities Unrecognized Gains, 12 months or longer	[2]	153	439
Obligations of States and Political Subdivisions [Member]
HTM Fair Value, Less than 12 months			196
HTM Unrealized Losses, Less than 12 months	[1]		(3)
HTM Unrecognized Gains, Less than 12 months	[2]		1
HTM Fair Value, 12 months or longer			0
HTM Unrealized Losses, 12 months or longer	[1]		0
HTM Unrecognized Gains, 12 months or longer	[2]		0
Asset-Backed Securities [Member]
HTM Fair Value, Less than 12 months		0	0
HTM Unrealized Losses, Less than 12 months	[1]	0	0
HTM Unrecognized Gains, Less than 12 months	[2]	0	0
HTM Fair Value, 12 months or longer		942	2,235
HTM Unrealized Losses, 12 months or longer	[1]	(157)	(455)
HTM Unrecognized Gains, 12 months or longer	[2]	153	439
AFS Fixed Income Securities [Member]
AFS Fair Value, Less than 12 months		737,456	461,125
AFS Unrealized Losses, Less than 12 months	[1]	(8,627)	(2,072)
AFS Fair Value, 12 months or longer		144,459	442,058
AFS Unrealized Losses, 12 months or longer	[1]	(2,760)	(8,170)
AFS Fixed Income Securities [Member] | U.S. Government and Government Agencies [Member]
AFS Fair Value, Less than 12 months		0	7,567
AFS Unrealized Losses, Less than 12 months	[1]	0	(13)
AFS Fair Value, 12 months or longer		399	10,866
AFS Unrealized Losses, 12 months or longer	[1]	(1)	(115)
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member]
AFS Fair Value, Less than 12 months		96,861	47,510
AFS Unrealized Losses, Less than 12 months	[1]	(545)	(105)
AFS Fair Value, 12 months or longer		0	64,018
AFS Unrealized Losses, 12 months or longer	[1]	0	(624)
AFS Fixed Income Securities [Member] | Corporate Securities [Member]
AFS Fair Value, Less than 12 months		430,481	276,648
AFS Unrealized Losses, Less than 12 months	[1]	(7,187)	(1,734)
AFS Fair Value, 12 months or longer		50,552	153,613
AFS Unrealized Losses, 12 months or longer	[1]	(1,695)	(4,075)
AFS Fixed Income Securities [Member] | Asset-Backed Securities [Member]
AFS Fair Value, Less than 12 months		55,856	113,202
AFS Unrealized Losses, Less than 12 months	[1]	(71)	(178)
AFS Fair Value, 12 months or longer		12,530	15,618
AFS Unrealized Losses, 12 months or longer	[1]	(34)	(195)
AFS Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]
AFS Fair Value, Less than 12 months		59,004	12,799
AFS Unrealized Losses, Less than 12 months	[1]	(367)	(34)
AFS Fair Value, 12 months or longer		15,561	59,219
AFS Unrealized Losses, 12 months or longer	[1]	(90)	(743)
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member]
AFS Fair Value, Less than 12 months		95,254	3,399
AFS Unrealized Losses, Less than 12 months	[1]	(457)	(8)
AFS Fair Value, 12 months or longer		65,417	138,724
AFS Unrealized Losses, 12 months or longer	[1]	(940)	(2,418)
Equity Securities [Member]
AFS Fair Value, Less than 12 months		142,163	5,262
AFS Unrealized Losses, Less than 12 months	[1]	(12,457)	(336)
AFS Fair Value, 12 months or longer		0	0
AFS Unrealized Losses, 12 months or longer	[1]	0	0
Common Stock [Member] | Equity Securities [Member]
AFS Fair Value, Less than 12 months		133,601	5,262
AFS Unrealized Losses, Less than 12 months	[1]	(12,340)	(336)
AFS Fair Value, 12 months or longer		0	0
AFS Unrealized Losses, 12 months or longer	[1]	0	$ 0
Preferred Stock [Member] | Equity Securities [Member]
AFS Fair Value, Less than 12 months		8,562
AFS Unrealized Losses, Less than 12 months	[1]	(117)
AFS Fair Value, 12 months or longer		0
AFS Unrealized Losses, 12 months or longer	[1]	$ 0

[1] Gross unrealized losses include non-OTTI unrealized amounts and OTTI losses recognized in AOCI. In addition, this column includes remaining unrealized gain or loss amounts on securities that were transferred to an HTM designation in the first quarter of 2009 for those securities that are in a net unrealized/unrecognized loss position.

[2] Unrecognized gains represent fair value fluctuations from the later of: (i) the date a security is designated as HTM; or (ii) the date that an OTTI charge is recognized on an HTM security.