Income Taxes - Components of Net Income Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2015	[1]	Sep. 30, 2015	[1]	Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2014	[2]	Sep. 30, 2014	[2]	Jun. 30, 2014	[2]	Mar. 31, 2014	[2]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of net income before income taxes
Domestic																	$ 93,390	$ 70,737	$ 63,278
Foreign																	2,951	(9,215)	(1,759)
Income before income taxes	$ 29,241		$ 27,943		$ 22,446		$ 16,711		$ 16,715		$ 10,064		$ 17,741		$ 17,002		$ 96,341	$ 61,522	$ 61,519

[1] During the first, second, third, and fourth quarters of 2015 we incurred restructuring expenses 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).

[2] During the first, third, and fourth quarters of 2014 we incurred restructuring expenses of $1.2 million, $7.8 million, and $4.9 million, respectively, or $0.02, $0.12, and $0.10 per diluted share (see Note 6).