Investments (Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	$ 2,522,950	$ 2,524,118
Gross Unrealized Gains, Debt securities	158,949	144,950
Gross Unrealized Losses, Debt securities	(15,924)	(32,402)
Fair Value, Debt securities	2,665,975	2,636,666
Amortized Cost, Equity securities		11,146
Gross Unrealized Gains, Equity securities		4,489
Gross Unrealized Losses, Equity securities		757
Fair Value, Equity securities		14,878
Amortized Cost	2,534,116	2,535,264
Gross Unrealized Gains	163,955	149,439
Gross Unrealized Losses	(16,409)	(33,159)
Fair Value	2,681,662	2,651,544
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	295,254	570,715
Less than 12 Months, Unrealized Losses	(10,555)	(28,639)
12 Months or Greater, Fair Value	115,419	47,633
12 Months or Greater, Unrealized Losses	(5,854)	(4,520)
Total, Fair Value	410,673	618,348
Total, Unrealized Losses	(16,409)	(33,159)
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,665,975	2,636,666
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	291,269	567,008
Less than 12 Months, Unrealized Losses	(10,070)	(27,882)
12 Months or Greater, Fair Value	115,390	47,633
12 Months or Greater, Unrealized Losses	(5,854)	(4,520)
Total, Fair Value	406,659	614,641
Total, Unrealized Losses	(15,924)	(32,402)
U.S. Agencies [Member]
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	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	0	0
Total, Unrealized Losses	0	0
U.S. Treasury [Member]
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	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	0	0
Total, Unrealized Losses	0	0
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	593	594
Gross Unrealized Gains, Debt securities	0	0
Gross Unrealized Losses, Debt securities	(64)	(110)
Fair Value, Debt securities	529	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	529	484
12 Months or Greater, Unrealized Losses	(64)	(110)
Total, Fair Value	529	484
Total, Unrealized Losses	(64)	(110)
Foreign Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	9,933	9,931
Gross Unrealized Gains, Debt securities	92	0
Gross Unrealized Losses, Debt securities	0	(156)
Fair Value, Debt securities	10,025	9,775
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	0	9,775
Less than 12 Months, Unrealized Losses	0	(156)
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	0	9,775
Total, Unrealized Losses	0	(156)
Public Utilities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	218,776	233,788
Gross Unrealized Gains, Debt securities	14,300	15,014
Gross Unrealized Losses, Debt securities	(818)	(1,397)
Fair Value, Debt securities	232,258	247,405
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	20,645	20,090
Less than 12 Months, Unrealized Losses	(790)	(1,343)
12 Months or Greater, Fair Value	987	962
12 Months or Greater, Unrealized Losses	(28)	(54)
Total, Fair Value	21,632	21,052
Total, Unrealized Losses	(818)	(1,397)
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	2,214,837	2,195,124
Gross Unrealized Gains, Debt securities	139,585	124,519
Gross Unrealized Losses, Debt securities	(15,037)	(30,732)
Fair Value, Debt securities	2,339,385	2,288,911
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	265,794	532,310
Less than 12 Months, Unrealized Losses	(9,275)	(26,376)
12 Months or Greater, Fair Value	113,874	46,187
12 Months or Greater, Unrealized Losses	(5,762)	(4,356)
Total, Fair Value	379,668	578,497
Total, Unrealized Losses	(15,037)	(30,732)
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	63,301	68,799
Gross Unrealized Gains, Debt securities	4,589	5,040
Gross Unrealized Losses, Debt securities	0	0
Fair Value, Debt securities	67,890	73,839
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	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	0	0
Total, Unrealized Losses	0	0
Home Equity [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	11,978	12,079
Gross Unrealized Gains, Debt securities	266	245
Gross Unrealized Losses, Debt securities	(5)	(7)
Fair Value, Debt securities	12,239	12,317
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	4,830	4,833
Less than 12 Months, Unrealized Losses	(5)	(7)
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	4,830	4,833
Total, Unrealized Losses	(5)	(7)
Manufactured Housing [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Debt securities	3,532	3,803
Gross Unrealized Gains, Debt securities	117	132
Gross Unrealized Losses, Debt securities	0	0
Fair Value, Debt securities	3,649	3,935
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	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	0	0
Total, Unrealized Losses	0	0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	15,687	14,878
Equity Public [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Equity securities	11,166
Gross Unrealized Gains, Equity securities	5,006
Gross Unrealized Losses, Equity securities	485
Fair Value, Equity securities	15,687
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	3,985	3,707
Less than 12 Months, Unrealized Losses	(485)	(757)
12 Months or Greater, Fair Value	29	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	4,014	3,707
Total, Unrealized Losses	$ (485)	$ (757)