Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income per consolidated statements of income	$ 29,349	$ 31,602	$ 59,669	$ 55,615
Unrealized gains (losses) on available for sale securities:
Unrealized holding gains/(losses) arising during the period	1,132	14,576	(784)	13,630
Less: adjustment for net gains/(losses) realized in net income	5	(32)	(643)	(36)
Pension and other postretirement benefit plans:
Change in the net actuarial loss during the period	980	753	1,960	1,506
Other comprehensive income	2,117	15,297	533	15,100
Comprehensive income	$ 31,466	$ 46,899	$ 60,202	$ 70,715