Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Consolidated Statements of Comprehensive Income [Abstract]
Net income		$ 58,902	$ 46,719	$ 160,183	$ 97,465
Other comprehensive income:
Net change in unrealized gain/loss on securities available for sale and hedges		5,949	(5,604)	19,794	39,997
Reclassification of net losses realized and included in earnings		1,374	1,158	4,479	2,960
Valuation adjustment for pension plan amendment	[1]			17,315
Other valuation adjustments for employee benefit plans		1,597	(6,347)	(9,185)	(6,347)
Amortization of unrealized net loss on securities transferred to held to maturity		977	1,108	2,726	2,736
Other comprehensive income/loss before income taxes		9,897	(9,685)	35,129	39,346
Income tax expense (benefit)		3,609	(3,537)	12,748	14,440
Other comprehensive income/loss net of income taxes		6,288	(6,148)	22,381	24,906
Comprehensive income		$ 65,190	$ 40,571	$ 182,564	$ 122,371

[1] For further discussion of the pension plan amendment, see Note 11 - Retirement Plans.