Consolidated Statements of Comprehensive Income - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Statement of Comprehensive Income [Abstract]    
Net earnings $ 20,083 $ 10,510
Other comprehensive income before tax:    
Net change in post-retirement benefit liability (2) (13)
Unrealized gains on investments(1):    
Unrealized holding (losses) gains arising during the period (18,344) 10,664
Less: Reclassification adjustments for losses (gains) included in net earnings 2,106 (509)
Unrealized (losses) gains on investments, net (16,238) 10,155
Other comprehensive (loss) income, before tax (16,240) 10,143
Income tax benefit (expense) related to components of other comprehensive income 3,410 (3,550)
Other comprehensive (loss) income, net of tax (12,829) 6,593
Comprehensive income $ 7,254 $ 17,102