Investments Investments (Summary of Unrealized Loss by 12 month Period) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Investments Unrealized Loss Position [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 6,715	$ 117,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(47)	(284)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	1,649
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(2)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	6,715	118,649
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(47)	(286)
Corporate Debt Securities [Member]
Investments Unrealized Loss Position [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	3,786	74,807
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2)	(212)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	1,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,786	75,807
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2)	(213)
Debt Securities Issued By The U.S Treasury And Other U.S Government Corporations And Agencies [Member]
Investments Unrealized Loss Position [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,248	38,004
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2)	(62)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	649
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,248	38,653
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2)	(63)
Debt Securities Issued By States Of The United States And Political Subdivisions Of The States [Member]
Investments Unrealized Loss Position [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,681	4,189
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(43)	(10)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,681	4,189
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (43)	$ (10)