CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net unrealized loss, tax benefit	$ 140	$ 14,900	$ 37,389
Reclassification of net realized loss, tax benefit	17,472	39,120	46,288
Pension and other postretirement benefits activity, tax (expense) benefit	$ (6,156)	$ (651)	$ 3,935