Stockholders' Equity (Details) - USD ($)	3 Months Ended				12 Months Ended			228 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Aug. 31, 2014
Stock Repurchase program
Common stock repurchased					$ 4,619,000	$ 7,894,000	$ 1,662,000
Dividends paid (in dollars per share)	$ 0.085	$ 0.085	$ 0.085	$ 0.085	$ 0.34	$ 0.34	$ 0.255
Stock repurchased under current and previously announced share repurchase programs								$ 1,200,000,000
Stock repurchased under current and previously announced share repurchase programs (in shares)								67,900,000
Common stock received by Company in lieu of cash from stock option exercises and vesting of non-vested shares (in shares)					170,567
Common stock received by Company in lieu of cash from stock option exercises and vesting of non-vested shares					$ 1,100,000
2012 Stock Repurchase program
Stock Repurchase program
Common stock repurchased (in shares)					900,000
Common stock repurchased					$ 4,600,000
Authorized amount to repurchase shares									$ 20,000,000
Amount available to repurchase additional shares	$ 11,400,000				$ 11,400,000			$ 11,400,000