CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 52,703	$ 36,418	$ 98,542	$ 66,924
Other comprehensive (loss) income, net of tax
Unrealized gain (loss) on debt securities arising during the period	24,510	(8,978)	48,015	(18,808)
Change in retirement obligation	246	494	536	817
Unrealized gain (loss) on derivatives	72	159	144	315
Other comprehensive income (loss)	24,828	(8,325)	48,695	(17,676)
Comprehensive income	$ 77,531	$ 28,093	$ 147,237	$ 49,248

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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