Summary of Discontinued Operations Presented in Consolidated Statements of Operations and Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Acquisitions And Discontinued Operations [Line Items]
Operating revenues	$ 0	$ 19,377	$ 173,447
Total operating expenses, net	0	27,630	147,012
Operating income (loss)	0	(8,253)	26,435
Other income (expense), net	0	(168)	(270)
Income (loss) from discontinued operations before tax	0	(8,421)	26,165
Provision for income taxes	0	7,759	21,481
Income (loss) from discontinued operations, net of tax	$ 0	$ (16,180)	$ 4,684