Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Net income	$ 1,215	[1]	$ 16,131	[1]	$ 17,622	[1]	$ 41,366	[1]	$ 7,379	[1]	$ 18,884	[1]	$ (41,313)	[1]	$ 21,846	[1]	$ 76,335	[1]	$ 6,794	[1]	$ 8,630
Change in fair value of interest rate swap agreements, net of tax																	0		0		16,274
Total Comprehensive Income																	$ 76,335		$ 6,794		$ 24,904

[1] The sum of the amounts for the four quarters does not equal the total for the year due to rounding.