Stockholders' Equity - Reconciliation of Number of Shares of Common Stock (Details) - shares	12 Months Ended			13 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Stockholders Equity Note [Abstract]
Common stock, beginning of period	45,721,000	48,297,000	52,169,000
Shares issued for stock options exercised	38,000	148,000	89,000
Shares of common stock issued upon lapse of RSUs	504,000	516,000	574,000
Common stock retired	(2,012,000)	(3,240,000)	(4,535,000)	(1,911,380)
Common stock, end of period	44,251,000	45,721,000	48,297,000	44,251,000