Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net Income	$ 39,227	$ 38,132
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized gain (loss) on securities	125	4,584
Reclassification adjustment for securities (gains) losses included in net income	(1,608)	(813)
Non-credit related unrealized gain (loss) on other-than-temporarily impaired debt securities	1,083	(135)
Unrealized gain on derivative financial instruments	34	34
Amortization (accretion) of net unrecognized pension and postretirement plan items	328	214
Other Comprehensive Income (Loss)	(38)	4,154
Total Comprehensive Income	$ 39,189	$ 42,286