Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 45,110	$ 33,826
Securities available for sale:
Unrealized holding gains (losses) on securities	11,317	(7,909)
Reclassification adjustment for gains realized in net income	(10)	0
Total securities	11,307	(7,909)
Derivative instruments:
Unrealized holding (losses) gains on derivative instruments	(915)	858
Total derivative instruments	(915)	858
Defined benefit pension and post-retirement benefit plans:
Amortization of net actuarial loss recognized in net periodic pension cost	54	66
Total defined benefit pension and post-retirement benefit plans	54	66
Other comprehensive income (loss), net of tax	10,446	(6,985)
Comprehensive income	$ 55,556	$ 26,841

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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