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	$ 47,014	$ 29,600	$ 93,072	$ 63,110
Unrealized holding gains (losses):
Before tax	38,237	(8,980)	64,989	(34,133)
Tax effect	(10,649)	2,535	(18,100)	9,507
Net of tax	27,588	(6,445)	46,889	(24,626)
Derivative Instruments
Before tax	2,441		3,899
Before tax		(590)		(68)
Tax effect	(680)		(1,086)
Tax effect		166		19
Net of tax	1,761		2,813
Net of tax		(424)		(49)
Total other comprehensive income (loss)	29,349	(6,869)	49,702	(24,675)
Total comprehensive income	$ 76,363	$ 22,731	$ 142,774	$ 38,435