Accumulated Other Comrehensive Loss (Components of AOCI) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ (122,294)		$ (135,192)
Other comprehensive income (loss) before reclassifications		(86,509)		9,479
Amounts reclassified from accumulated other comprehensive loss	[1]	23,667		3,419
Net current period other comprehensive income (loss)		(62,842)		12,898	$ (70,752)
Cumulative effect adjustments						$ (50,051)
Ending balance		(235,187)		(122,294)	(135,192)
Unrealized losses on securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[2]	(30,945)		(45,875)
Other comprehensive income (loss) before reclassifications	[2]	22,461		17,635
Amounts reclassified from accumulated other comprehensive loss	[1],[2]	(270)		(2,705)
Net current period other comprehensive income (loss)	[2]	22,191		14,930
Cumulative effect adjustments						(29,751)
Ending balance	[2]	(38,505)		(30,945)	(45,875)
Unrealized losses on securities available for sale transferred to held to maturity
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[2]	0		0
Other comprehensive income (loss) before reclassifications	[2]	(84,321)		0
Amounts reclassified from accumulated other comprehensive loss	[2]	13,172	[1]	0
Net current period other comprehensive income (loss)	[2]	(71,149)		0
Cumulative effect adjustments						0
Ending balance	[2]	(71,149)		0	0
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[2]	(91,349)		(89,317)
Other comprehensive income (loss) before reclassifications	[2]	(24,649)		(8,156)
Amounts reclassified from accumulated other comprehensive loss	[1],[2]	10,765		6,124
Net current period other comprehensive income (loss)	[2]	(13,884)		(2,032)
Cumulative effect adjustments						$ (20,300)
Ending balance	[2]	$ (125,533)		$ (91,349)	$ (89,317)

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

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