Shareholders' Equity (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended	29 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2016	Feb. 23, 2017
Shareholders' Equity [Abstract]
Stock Repurchase Program Authorized Percent Of Common Stock				5.00%
Stock Repurchase Program, Number of Shares Authorized to be Repurchased				921,000
Treasury Stock, Shares, Acquired	0	1,398,026	2,519,584
Treasury Stock, Amount, Acquired		$ 22.1	$ 40.8