Stockholders' Equity - Repurchase (Details) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Oct. 23, 2002
Class of Stock Disclosures
Number of shares of outstanding common stock authorized to be repurchased			3,000,000
Purchases made pursuant to repurchase authorization (in shares)	0	0
Number of remaining shares of common stock authorized to be repurchased	1,653,333