CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 150,952	$ 175,459	$ 156,959
Other comprehensive income:
Net unrealized appreciation (depreciation) of investment securities during the year, net of income taxes of $3,195, $(2,120) and $2,028, respectively	5,444	(3,635)	3,493
Valuation allowance on investment securities' deferred tax asset during the year	2,024	(2,955)	963
Pension and postretirement benefits, net of income taxes of $(2,532), $(13,232) and $628, respectively	(4,157)	(22,062)	1,061
Reclassification adjustments for amounts included in net income, net of income taxes of $(1,162), $(830) and $(1,139), respectively	(2,001)	(1,428)	(1,980)
Total other comprehensive income	1,310	(30,080)	3,537
Comprehensive income	$ 152,262	$ 145,379	$ 160,496