Stock Plans (LTIP Target Performance Shares) (Details) - Performance Shares [Member] - shares				12 Months Ended
	Feb. 16, 2017	Feb. 11, 2016	Feb. 25, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at beginning of period (in shares)				190,000	168,000	179,000
Shares granted (in shares)	157,400	1,669,000	665,000	211,000	111,000	49,000
Shares vested (in shares)				(41,000)	(59,000)	(50,000)
Shares forfeited (in shares)				(54,000)	(30,000)	(10,000)
Balance at end of period (in shares)				306,000	190,000	168,000