Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net Income	$ 41,582	$ 39,324	$ 119,605	$ 109,494
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized gain (loss) on securities	10,834	(1,876)	4,714	15,143
Reclassification adjustment for securities (gains) losses included in net income	(28)	288	(1,840)	(979)
Non-credit related unrealized gain (loss) on other-than-temporarily impaired debt securities	271	(542)	234	187
Unrealized gain on derivative financial instruments	34	34	102	102
Amortization (accretion) of net unrecognized pension and postretirement plan items	214	(13)	642	(37)
Other Comprehensive Income (Loss)	11,325	(2,109)	3,852	14,416
Total Comprehensive Income	$ 52,907	$ 37,215	$ 123,457	$ 123,910