Earnings Per Share (Details) - shares	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
Basic computation	48,329,000	48,315,000	48,309,000	48,242,000		48,098,000	47,065,000	47,044,000	46,977,000	48,298,896		47,298,350	40,156,177
Performance share awards (1)				22,044	[1]					176,166	[1]	344,451
Diluted computation										48,475,062		47,642,801

[1] Performance share awards are included in diluted weighted average number of shares outstanding based upon what would be issued if the end of the most recent reporting period was the end of the term of the award. We adopted the provisions of ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, during the fourth quarter of 2016. Under this ASU, the assumed proceeds from applying the treasury stock method when computing earnings per share no longer includes the amount of excess tax benefits or deficiencies that used to be recognized as additional paid-in capital. This change in the treasury stock method was made on a prospective basis, with adjustments reflected as of January 1, 2016. The changes to the treasury stock method required by this ASU increased dilutive shares by 22,044 shares for the year ended December 31, 2016. See Note 2 - Significant Accounting Policies, for further discussion of the impacts of this standard.