Investments (Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Total	$ 2,577,275
Fair Value, Debt securities	2,711,377
Amortized Cost	2,590,074	2,535,264
Gross Unrealized Gains	148,083	149,439
Gross Unrealized Losses	(9,477)	(33,159)
Fair Value	2,728,680	2,651,544
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	100,678	570,715
Less than 12 Months, Unrealized Losses	(3,042)	(28,639)
12 Months or Greater, Fair Value	211,706	47,633
12 Months or Greater, Unrealized Losses	(6,435)	(4,520)
Total, Fair Value	312,384	618,348
Total, Unrealized Losses	(9,477)	(33,159)
Debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	2,577,275	2,524,118
Gross Unrealized Gains, Debt securities	143,234	144,950
Gross Unrealized Losses, Debt securities	(9,132)	(32,402)
Fair Value, Debt securities	2,711,377	2,636,666
Fair Value	2,711,377	2,636,666
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	100,373	567,008
Less than 12 Months, Unrealized Losses	(2,990)	(27,882)
12 Months or Greater, Fair Value	207,905	47,633
12 Months or Greater, Unrealized Losses	(6,142)	(4,520)
Total, Fair Value	308,278	614,641
Total, Unrealized Losses	(9,132)	(32,402)
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	589	594
Gross Unrealized Gains, Debt securities	0	0
Gross Unrealized Losses, Debt securities	(36)	(110)
Fair Value, Debt securities	553	484
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	0	0
Less than 12 Months, Unrealized Losses	0	0
12 Months or Greater, Fair Value	553	484
12 Months or Greater, Unrealized Losses	(36)	(110)
Total, Fair Value	553	484
Total, Unrealized Losses	(36)	(110)
Foreign Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	9,939	9,931
Gross Unrealized Gains, Debt securities	386	0
Gross Unrealized Losses, Debt securities	0	(156)
Fair Value, Debt securities	10,325	9,775
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value		9,775
Less than 12 Months, Unrealized Losses		(156)
12 Months or Greater, Fair Value		0
12 Months or Greater, Unrealized Losses		0
Total, Fair Value		9,775
Total, Unrealized Losses		(156)
Public Utilities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	169,179	233,788
Gross Unrealized Gains, Debt securities	10,163	15,014
Gross Unrealized Losses, Debt securities	(126)	(1,397)
Fair Value, Debt securities	179,216	247,405
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	0	20,090
Less than 12 Months, Unrealized Losses	0	(1,343)
12 Months or Greater, Fair Value	14,827	962
12 Months or Greater, Unrealized Losses	(126)	(54)
Total, Fair Value	14,827	21,052
Total, Unrealized Losses	(126)	(1,397)
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	2,334,700	2,195,124
Gross Unrealized Gains, Debt securities	128,280	124,519
Gross Unrealized Losses, Debt securities	(8,961)	(30,732)
Fair Value, Debt securities	2,454,019	2,288,911
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	100,373	532,310
Less than 12 Months, Unrealized Losses	(2,990)	(26,376)
12 Months or Greater, Fair Value	187,699	46,187
12 Months or Greater, Unrealized Losses	(5,971)	(4,356)
Total, Fair Value	288,072	578,497
Total, Unrealized Losses	(8,961)	(30,732)
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	48,674	68,799
Gross Unrealized Gains, Debt securities	4,116	5,040
Gross Unrealized Losses, Debt securities	0	0
Fair Value, Debt securities	52,790	73,839
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value		0
Less than 12 Months, Unrealized Losses		0
12 Months or Greater, Fair Value		0
12 Months or Greater, Unrealized Losses		0
Total, Fair Value		0
Total, Unrealized Losses		0
Home Equity [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	11,702	12,079
Gross Unrealized Gains, Debt securities	225	245
Gross Unrealized Losses, Debt securities	(9)	(7)
Fair Value, Debt securities	11,918	12,317
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	0	4,833
Less than 12 Months, Unrealized Losses	0	(7)
12 Months or Greater, Fair Value	4,826	0
12 Months or Greater, Unrealized Losses	(9)	0
Total, Fair Value	4,826	4,833
Total, Unrealized Losses	(9)	(7)
Manufactured Housing [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	2,492	3,803
Gross Unrealized Gains, Debt securities	64	132
Gross Unrealized Losses, Debt securities	0	0
Fair Value, Debt securities	2,556	3,935
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	17,303	14,878
Equity Public [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Equity securities	12,799	11,146
Gross Unrealized Gains, Equity securities	4,849	4,489
Gross Unrealized Losses, Equity securities	(345)	(757)
Fair Value, Equity securities	17,303	14,878
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	305	3,707
Less than 12 Months, Unrealized Losses	(52)	(757)
12 Months or Greater, Fair Value	3,801	0
12 Months or Greater, Unrealized Losses	(293)	0
Total, Fair Value	4,106	3,707
Total, Unrealized Losses	$ (345)	$ (757)