Investments (Repurchase Agreement and Securities Lending) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	$ 10,334	$ 11,063
Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	10,334	11,063
Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
30 days or greater
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
US Treasury securities and obligations of U.S. government authorities and agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	3,109	8,169
US Treasury securities and obligations of U.S. government authorities and agencies | Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	3,109	8,169
US Treasury securities and obligations of U.S. government authorities and agencies | Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	2,121	0
Foreign government bonds | Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	2,121	0
Foreign government bonds | Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
U.S. public corporate securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	2,745	628
U.S. public corporate securities | Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	2,745	628
U.S. public corporate securities | Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
Foreign public corporate securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	2,359	2,266
Foreign public corporate securities | Overnight & Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	2,359	2,266
Foreign public corporate securities | Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total cash collateral for loaned securities	$ 0	$ 0