Income Taxes - Components of Net Income from Continuing Operations Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2016	[1]	Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	[2]	Sep. 30, 2015	[2]	Jun. 30, 2015	[2]	Mar. 31, 2015	[2]	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of net income before income taxes
Domestic																	$ 98,966	$ 93,390	$ 70,737
Foreign																	1,033	2,951	(9,215)
Income before income taxes	$ 19,461		$ 30,159		$ 17,285		$ 33,094		$ 29,241		$ 27,943		$ 22,446		$ 16,711		$ 99,999	$ 96,341	$ 61,522

[1] During the first, second, and fourth quarters of 2016 we incurred restructuring and reorganization charges of $(5.7) million, $5.3 million, and $1.0 million, respectively, or $(0.11), $0.10, and $0.02 per diluted share. The negative restructuring and reorganization charges in the first quarter reflect the gain on disposition of business operations (see Note 6).

[2] During the first, second, third, and fourth quarters of 2015 we incurred restructuring and reorganization charges of $0.6 million, $0.4 million, $0.8 million, and $1.3 million, respectively, or $0.01, $0.01, $0.02, and $0.03 per diluted share (see Note 6).