Summary of Significant Accounting Policies - Schedule of Earnings Per Share (Detail) (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
Earnings Per Share [Abstract]
Earnings from continuing operations	$ (3,043)	$ 9,006	$ 6,874	$ 7,692	$ 1,183	$ 13,759	$ 6,968	$ 5,506	$ 20,529	$ 27,416	$ 13,775
Less dividend equivalents attributable to RSUs outstanding									(320)	(252)	(89)
Earnings from continuing operations attributable to common shareholders									20,209	27,164	13,686
Earnings (loss) from discontinued operations									2,889	42,595	(1,328)
Less dividend equivalents attributable to RSUs outstanding									(71)	(392)	(45)
Earnings (loss) from discontinued operations attributable to common shareholders									2,818	42,203	(1,373)
Net earnings attributable to common shareholders used for basic and diluted earnings per share calculation									$ 23,027	$ 69,367	$ 12,313
Basic									33,409	33,397	33,395
Stock options									0	0	0
Diluted									33,409	33,397	33,395
RSUs outstanding at the end of the period	333				296				333	296	216