Stockholders' Equity - Stock Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	2 Months Ended	12 Months Ended
	Sep. 30, 2018	Feb. 25, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stockholders’ Equity
Average purchase price per share for share repurchase (in dollars per share)			$ 17.82	$ 17.46
Aggregate cost		$ 7,100	$ 93,369	$ 147,422	$ 14,820
Remaining authorized repurchase amount			$ 42,900
Common Stock
Stockholders’ Equity
Shares repurchased during the period (in shares)		471,500	5,238,566	8,450,294	995,650
Treasury stock, shares, retired (in shares)	5,238,566			8,450,294
Retirement of treasury stock	$ 93,400		$ 93,369	$ 147,422	$ 320,109