Accumulated Other Comprehensive Loss (Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses)		$ 351		$ 4,293		$ 26,673
Income taxes		(103,297)		(219,946)		$ (125,585)
Amounts reclassified from accumulated other comprehensive income, net of tax	[1]	23,667		3,419
Unrealized losses on securities available for sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses)	[1]	351		4,293
Income taxes	[1]	(81)		(1,588)
Amounts reclassified from accumulated other comprehensive income, net of tax	[1],[2]	(270)		(2,705)
Unrealized losses on securities available for sale transferred to held to maturity
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	[1]	(17,106)
Income taxes	[1]	3,934
Amounts reclassified from accumulated other comprehensive income, net of tax	[2]	13,172	[1]	0
Defined Benefit Pension Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Employee Benefits, prior service costs	[1]	79		210
Reclassification adjustment for losses included in income before income taxes	[1]	13,902		9,510
Total before taxes		13,981		9,720	[1]
Income taxes	[1]	3,216		3,596
Amounts reclassified from accumulated other comprehensive income, net of tax	[1],[2]	$ 10,765		$ 6,124

[1] Amounts in parentheses indicate debits to profit/loss.

[2] All amounts are net of tax. Amounts in parentheses indicate debits.