Investments Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	$ 162,217	$ 152,784
Less than 12 Months, Gross Unrealized Losses	381	126
Twelve Months or Longer, Fair Value	0	0
12 Months or Longer, Gross Unrealized Losses	0	0
Fair Value	162,217	152,784
Gross Unrealized Losses	381	126
Securities and obligations of U.S. government agencies
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	110,345	152,784
Less than 12 Months, Gross Unrealized Losses	323	126
Twelve Months or Longer, Fair Value	0	0
12 Months or Longer, Gross Unrealized Losses	0	0
Fair Value	110,345	152,784
Gross Unrealized Losses	$ 323	$ 126