Stockholders' Equity (Treasury stock activity) (Details) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Stockholders' Equity Note [Abstract]
Beginning balance (in shares)	59,356	54,626
Stock awards (in shares)	(734)	(466)
Treasury stock purchases (in shares)	1,889	2,235
Ending balance (in shares)	60,511	56,395