Accumulated Other Comprehensive Income - Roll Forward (Details) - Accumulated Other Comprehensive Income (Loss) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in accumulated other comprehensive income
Beginning balance	$ (563)	$ 2,993	$ 2,993	$ 1,017	$ (459)
Effect of equity accounting guidance adoption	(3,215)
Adjusted beginning balance	(222)	1,017	1,017	(459)
Other comprehensive income (loss) before reclassification	6,444	(1,137)	(740)	2,834	2,708
Federal income (taxes) benefit	(917)	28	76	(772)	(899)
Other comprehensive income (loss) before reclassification, net of tax	5,527	(1,109)	(664)	2,062	1,809
Amounts reclassified from AOCI	(53)	146	399	(608)	(499)
Federal income taxes	11	(27)	(76)	68	166
Amounts reclassified from AOCI, net of tax	(42)	119	323	(540)	(333)
Other comprehensive income (loss)	5,485	(990)	(341)	1,522	1,476
Ending balance	$ 4,922	$ (1,212)	$ (563)	$ 2,993	$ 1,017

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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