Equity - Additional Information (Details) - USD ($)			3 Months Ended
	Mar. 20, 2019	Apr. 01, 2015	Mar. 31, 2019	Mar. 31, 2018
Stockholders Equity Note [Line Items]
Dividends declared and paid per share (usd per share)	$ 0.05
Dividend equivalents paid			$ 300,000	$ 300,000
Purchase of treasury stock			24,401,000	34,753,000
Cogent Partners, LP
Stockholders Equity Note [Line Items]
Business acquisition, equity interest issued or issuable (in shares)		779,454
Conditional consideration (shares)		334,048
Additional Paid-in Capital | Cogent Partners, LP
Stockholders Equity Note [Line Items]
Contingent consideration classified as equity		$ 11,900,000
Restricted Stock Units
Stockholders Equity Note [Line Items]
Treasury stock, value, acquired, cost method			$ 12,700,000	$ 6,700,000
Restricted stock units vested and issued as common stock (shares)			1,219,545	918,073
Repurchased shares for award (shares)			499,786	361,453
Average repurchase price of shares for award (usd per share)			$ 25.50	$ 18.40
Common Stock
Stockholders Equity Note [Line Items]
Treasury stock, value, acquired, cost method			$ 436,885
Treasury stock acquired, average cost per share			$ 26.68
Purchase of treasury stock			$ 11,700,000