Accumulated Other Comprehensive Income - Tax Amounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Tax benefit (expense) on change in unrealized components of defined benefit plans:
Tax benefit on net actuarial loss arising during the period	$ 41,012	$ 98,642	$ 13,242
Other comprehensive income (loss), tax effect from pension and OPEB amortization	(10,016)	(6,414)	(6,037)
Tax expense on settlements and other	0	0	(413)
Tax benefit on other comprehensive loss	$ 30,996	$ 92,228	$ 6,792