Accumulated Other Comprehensive Loss (Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Long-term obligations		$ 924,905	$ 710,097		$ 740,186
Securities gains (losses)		10,817	29,096		0
Income taxes		(122,028)	(65,032)		$ (101,574)
Amounts reclassified from accumulated other comprehensive income, net of tax	[1]	(81)	(14,598)
Unrealized Loss on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive income, net of tax	[2]	0	0
Unrealized Gains on Investment Securities Available for Sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses)	[1]	10,817	29,096
Income taxes	[1]	(4,138)	(11,224)
Amounts reclassified from accumulated other comprehensive income, net of tax	[1],[2]	(6,679)	(17,872)
Defined Benefit Pension Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Employee Benefits, prior service costs	[1]	(210)	(210)
Reclassification adjustment for losses included in income before income taxes	[1]	(11,376)	(5,148)
Total before taxes		(11,586)	(5,358)	[1]
Income taxes	[1]	4,988	2,084
Amounts reclassified from accumulated other comprehensive income, net of tax	[1],[2]	$ 6,598	$ 3,274

[1] (Dollars in thousands) Year ended December 31, 2015Details about accumulated other comprehensive income (loss) Amount reclassified from accumulated other comprehensive income (loss)(1) Affected line item in the statement where net income is presentedUnrealized gains and losses on available for sale securities $10,817 Securities gains (4,138) Income taxes $6,679 Net income Amortization of defined benefit pension items Prior service costs $(210) Employee benefitsActuarial losses (11,376) Employee benefits (11,586) Employee benefits 4,988 Income taxes $(6,598) Net incomeTotal reclassifications for the period $81 Year ended December 31, 2014Details about accumulated other comprehensive income (loss) Amount reclassified from accumulated other comprehensive income (loss)(1) Affected line item in the statement where net income is presentedUnrealized gains and losses on available for sale securities $29,096 Securities gains (11,224) Income taxes $17,872 Net income Amortization of defined benefit pension items Prior service costs $(210) Employee benefitsActuarial losses (5,148) Employee benefits (5,358) Employee benefits 2,084 Income taxes $(3,274) Net incomeTotal reclassifications for the period $14,598 (1) Amounts in parentheses indicate debits to profit/loss.

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