Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income per consolidated statements of income	$ 29,904	$ 26,968	$ 89,573	$ 82,583
Unrealized gains (losses) on available for sale securities:
Unrealized holding gains/(losses) arising during the period	2,618	15,205	1,834	28,835
Less: adjustment for net gains/(losses) realized in net income	0	(20)	(643)	(56)
Pension and other postretirement benefit plans:
Change in the net actuarial loss during the period	976	747	2,936	2,253
Other comprehensive income	3,594	15,932	4,127	31,032
Comprehensive income	$ 33,498	$ 42,900	$ 93,700	$ 113,615