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
Net income	$ 111,586	$ 111,341	$ 228,082	$ 217,821
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	158,140	(11,884)	356,286	(190,788)
Change in net unrealized gain on securities transferred to held to maturity	(308)	(2,041)	(652)	(4,660)
Reclassification adjustment for net (gains) losses included in net income	(169)	60	(169)	79
Total securities available for sale and transferred securities, before tax amount	157,663	(13,865)	355,465	(195,369)
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)	1,406	1,251	2,812	2,501
Total defined-benefit post-retirement benefit plans	1,406	1,251	2,812	2,501
Other comprehensive income (loss), before tax	159,069	(12,614)	358,277	(192,868)
Deferred tax expense (benefit) related to other comprehensive income	33,405	(2,649)	75,239	(40,502)
Other comprehensive income (loss), net of tax	125,664	(9,965)	283,038	(152,366)
Comprehensive income (loss)	$ 237,250	$ 101,376	$ 511,120	$ 65,455