Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Other Comprehensive Income [Abstract]
Increase (decrease) in estimated fair value of investment in debt securities, tax	$ 3,208	$ (1,162)	$ 1,710
Unrecognized actuarial loss and prior service cost, income taxes	(10,439)	699	10,293
Income tax on cash flow hedge activity	$ (238)	$ (66)	$ 21