Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 22,640	$ 56,276
Change in debt securities available-for-sale:
Unrealized holding gains (losses) for the period	103,954	62,265
Reclassification adjustment for securities (gains) losses realized in income	(5,174)	103
Income tax effect	(22,411)	(14,578)
Unrealized gains (losses) on available-for-sale debt securities	76,369	47,790
Change in securities held-to-maturity:
Amortization of unrealized losses on securities transferred from available-for-sale	0	457
Income tax effect	0	(106)
Changes from securities held-to-maturity	0	351
Cash flow hedges:
Net unrealized derivative gains (losses) on cash flow hedges	7,803	(392)
Reclassification adjustment for (gains) losses realized in net income	(431)	(385)
Income tax effect	(1,811)	191
Changes from cash flow hedges	5,561	(586)
Defined benefit pension plans:
Amortization of net loss recognized in income	27	20
Income tax effect	(7)	(5)
Changes from defined benefit pension plans	20	15
Other comprehensive income (loss), net of tax	81,950	47,570
Comprehensive income	$ 104,590	$ 103,846