Equity (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		2 Months Ended	3 Months Ended								12 Months Ended
	Dec. 20, 2017	Apr. 01, 2015	Nov. 30, 2017	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity, Class of Treasury Stock [Line Items]
Cost of repurchased common stock														$ 79,561	$ 28,186	$ 11,902
Dividends paid to stockholders (in dollars per share)	$ 0.05													$ 1.4	$ 1.80	$ 1.80
Dividends declared per common share (usd per share)						$ 0.05	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 1.40	$ 1.8	$ 1.80
Dividend equivalents paid on outstanding restricted stock units														$ 6,300	$ 8,500	$ 6,500
Common stock
Equity, Class of Treasury Stock [Line Items]
Repurchased common stock (shares)															891,017
Average repurchase price of common stock (usd per share)															$ 22.63
Restricted stock units
Equity, Class of Treasury Stock [Line Items]
Restricted stock units vested and issued as common stock (shares)									1,023,132					1,197,260	852,218
Repurchased shares for award (shares)														491,677	319,573
Average repurchase price of shares for award (usd per share)														$ 28.04	$ 25.10
Cogent Partners, LP
Equity, Class of Treasury Stock [Line Items]
Common stock issued on acquisition date (in shares)		779,454
Possible contingent consideration (shares)		334,048
Fair value of contingent common shares		$ 11,900
Chairman and Chief Executive Officer
Equity, Class of Treasury Stock [Line Items]
Company stock sold, total			$ 20,000
Total common shares issued (in shares)			1,159,420
Chairman
Equity, Class of Treasury Stock [Line Items]
Company stock sold per transaction			$ 10,000
Chief Executive Officer
Equity, Class of Treasury Stock [Line Items]
Company stock sold per transaction			$ 10,000
Term loan | Secured debt | Recapitalization credit agreement
Equity, Class of Treasury Stock [Line Items]
Amount borrowed				$ 350,000
Common stock
Equity, Class of Treasury Stock [Line Items]
Repurchased common stock (shares)					343,411
Share repurchase program, September 2017 | Common stock
Equity, Class of Treasury Stock [Line Items]
Authorized repurchase amount (up to)							$ 285,000
Repurchased common stock (shares)				3,434,137		3,777,548
Average repurchase price of common stock (usd per share)				$ 17.25										$ 17.41
Cost of repurchased common stock				$ 59,200		$ 65,800
Fees and expenses related to tender offer				$ 700
Remaining authorization under share repurchase plan					$ 219,200	$ 219,200								$ 219,200