Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net income	$ 111,341	$ 85,553	$ 217,821	$ 170,494
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	(11,884)	90,390	(190,788)	124,201
Change in net unrealized gain on securities transferred to held to maturity	(2,041)	(3,860)	(4,660)	(10,146)
Reclassification adjustment for net (gains) losses included in net income	60	50	79	50
Total securities available for sale and transferred securities, before tax amount	(13,865)	86,580	(195,369)	114,105
Defined-benefit post-retirement benefit plans:
Change in the net actuarial gain/loss	0	0	0	0
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit)	1,251	1,358	2,501	2,715
Total defined-benefit post-retirement benefit plans	1,251	1,358	2,501	2,715
Other comprehensive income (loss), before tax	(12,614)	87,938	(192,868)	116,820
Deferred tax expense (benefit) related to other comprehensive income	(2,649)	30,778	(40,502)	40,887
Other comprehensive income (loss), net of tax	(9,965)	57,160	(152,366)	75,933
Comprehensive income (loss)	$ 101,376	$ 142,713	$ 65,455	$ 246,427