Equity (Details) - USD ($)		1 Months Ended	12 Months Ended			26 Months Ended
	Apr. 01, 2015	Nov. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Apr. 30, 2019	Sep. 30, 2017
Equity, Class of Treasury Stock [Line Items]
Cost of repurchased common stock			$ 69,439,000	$ 195,299,000	$ 79,561,000
Dividends declared per common share (usd per share)			$ 0.20	$ 0.20	$ 1.40
Dividend equivalents paid on outstanding restricted stock units			$ 1,300,000	$ 1,100,000	$ 6,300,000
Common stock
Equity, Class of Treasury Stock [Line Items]
Repurchased common stock (shares)			3,275,641	7,497,635	3,777,548
Average repurchase price of common stock (usd per share)			$ 16.93	$ 24.89	$ 17.41
Cost of repurchased common stock			$ 55,500,000		$ 65,800,000
Restricted stock units
Equity, Class of Treasury Stock [Line Items]
Restricted stock units vested and issued as common stock (shares)			1,407,095	1,238,733
Repurchased shares for award (shares)			573,472	433,507
Average repurchase price of shares for award (usd per share)			$ 24.37	$ 20.00
Treasury stock, value, acquired, cost method			$ 14,000,000.0	$ 8,700,000
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	$ 11,900,000
Chairman
Equity, Class of Treasury Stock [Line Items]
Company stock sold per transaction		$ 10,000,000.0
Company stock sold, total		$ 20,000,000.0
Total common shares issued (in shares)		1,159,420
Common stock
Equity, Class of Treasury Stock [Line Items]
Cost of repurchased common stock				186,600,000
Share repurchase program, September 2017 | Common stock
Equity, Class of Treasury Stock [Line Items]
Authorized repurchase amount (up to)								$ 285,000,000
Repurchased common stock (shares)						14,550,824
Average repurchase price of common stock (usd per share)						$ 21.16
Cost of repurchased common stock						$ 307,900,000
Fees and expenses related to tender offer				$ 200,000	$ 700,000
Remaining authorization under share repurchase plan			$ 31,200,000			$ 31,200,000
Stock Repurchase Program Authorized in April 2019 | Common stock
Equity, Class of Treasury Stock [Line Items]
Authorized repurchase amount (up to)							$ 339,100,000
Increase (decrease) In authorized amount							$ 75,000,000.0