Statement of Comprehensive Income Statement (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income	$ 183,684	$ 134,106	$ 119,558
Changes in unrealized securities' holding gains and (losses), net of taxes of $46.6 million, $2.2 million, and $10.2 million, respectively	(86,537)	4,154	26,205
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	(1,822)	2,461	7,203
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(84,715)	1,693	19,002
Cumulative net loss	31,161	(795)	(21,744)
Other Comprehensive Income (Loss), Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service (Cost) Credit, Net of Tax	(1)	(52)	256
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	2,884	6,836	4,702
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	34,044	5,989	(16,786)
Other Comprehensive Income (Loss), Net of Tax	(50,671)	7,682	2,216
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 133,013	$ 141,788	$ 121,774