Consolidated Statements of Comprehensive Income (unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net income	$ 27,640	$ 16,916	$ 45,649	$ 24,565
Other comprehensive income (loss), net of tax
Unrealized net holding gains (losses) arising during the period (pre-tax amounts of $8,267, ($24,712), $16,892 and ($26,464))	4,992	(14,923)	10,200	(15,978)
Reclassification adjustment for net gains related to securities available for sale included in net income (pre-tax amounts of $14, ($61), $21 and $1,084)	(8)	37	(13)	(650)
Pension and other benefits:
Amortization of prior service cost and actuarial gains (pre-tax amounts of $19, $710, $38 and $1,536)	11	426	23	922
Total other comprehensive income (loss)	4,995	(14,460)	10,210	(15,706)
Comprehensive income	$ 32,635	$ 2,456	$ 55,859	$ 8,859