Significant Accounting Policies (Details) - shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Weighted Average Number of Shares Outstanding, Basic	44,113	44,110	43,297	42,380	42,355	42,517	42,790	43,340	43,479	42,747	44,362
Incremental Common Shares Attributable to Contingently Issuable Shares									127	98	110
Weighted Average Number of Shares, Restricted Stock									64	63	128
Weighted Average Number of Shares Outstanding, Diluted	44,326	44,320	43,505	42,520	42,518	42,685	42,959	43,466	43,670	42,908	44,600