Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
	Sep. 18, 2019	Apr. 01, 2015	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stockholders Equity Note [Line Items]
Dividends declared and paid per share (usd per share)	$ 0.05				$ 0.15	$ 0.15
Dividend equivalents paid					$ 1,000	$ 800
Purchase of treasury stock					$ 46,262	$ 177,786
Cogent Partners, LP
Stockholders Equity Note [Line Items]
Business acquisition, equity interest issued or issuable (in shares)		779,454
Conditional consideration (shares)		334,048	334,048	334,048	334,048	334,048
Additional paid-in capital | Cogent Partners, LP
Stockholders Equity Note [Line Items]
Contingent consideration classified as equity		$ 11,900
Restricted Stock Units
Stockholders Equity Note [Line Items]
Restricted stock units vested and issued as common stock (shares)					1,368,985	1,145,849
Repurchased shares for award (shares)					557,255	428,798
Average repurchase price of shares for award (usd per share)					$ 24.53	$ 19.97
Treasury stock, value, acquired, cost method					$ 13,700	$ 8,600
Common stock, par value $0.01 per share
Stockholders Equity Note [Line Items]
Treasury stock, shares, acquired (shares)					1,841,396	6,810,797
Treasury stock acquired, average cost per share (usd per share)					$ 17.70	$ 24.85
Purchase of treasury stock					$ 32,600	$ 169,200