CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net income (loss)	$ 74,428	$ 72,017	$ 45,522	$ 59,982	$ (1,407)	$ 12,114	$ 12,375	$ (72,930)	$ 251,949	$ (49,848)	$ (927,079)
Other comprehensive income (loss), net of tax (note 12):
Change in unrealized investment gains and losses (note 6)									91,139	(123,591)	(78,659)
Benefit plans adjustment (note 13)									(52,112)	68,038	(1,221)
Foreign currency translation adjustment									(2,642)	(14,010)	1,593
Other comprehensive income (loss), net of tax									36,385	(69,563)	(78,287)
Comprehensive income (loss)									$ 288,334	$ (119,411)	$ (1,005,366)