Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net Income	$ 39,596	$ 40,582	$ 81,379	$ 79,809
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized gain (loss) on securities	12,990	(36,958)	26,923	(36,833)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net (Gain) Loss, Net of Tax	0	0	(944)	0
Reclassification adjustment for securities (gains) losses included in net income	(723)	(1,862)	(723)	(3,470)
Non-credit related unrealized gain (loss) on other-than-temporarily impaired debt securities	323	355	512	1,438
Unrealized gain on derivative financial instruments	34	34	68	68
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	0	0	2,144	0
Amortization (accretion) of net unrecognized pension and postretirement plan items	104	328	200	656
Other Comprehensive Income (Loss)	12,728	(38,103)	28,180	(38,141)
Total Comprehensive Income	$ 52,324	$ 2,479	$ 109,559	$ 41,668