Stockholders' Equity - Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	Apr. 27, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Components of basic and diluted earnings per share
Net income		$ 23,307	$ 33,695	$ 56,363	$ 70,663
Weighted average shares outstanding - basic and diluted		83,611,000	82,947,000	83,843,000	82,526,000
Earnings per share:
Earnings per share, basic and diluted (in dollars per share)		$ 0.28	$ 0.41	$ 0.67	$ 0.86
Dividends
Dividends accrued, per share (in dollars per share)	$ 0.46			$ 0.92
Dividends to be paid		$ 38,500		$ 38,500
Common stock repurchases
Shares repurchased in the open market or privately		237,472	1,075,826	714,354	2,201,497
Shares repurchased from employees to cover minimum income tax withholdings		237,472	300,826	239,354	304,497