Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 148,732
Stock based-awards			18,533
Repurchase of common shares			(4,777)
Dividends paid			(72,929)
Non-controlling interest additions			(10)
Amortization of deferred pension costs, net of tax			145
Interest rate swaps, net of tax			931
Net income	$ 22,405	$ 21,053	70,787	$ 61,444
Ending balance	161,412		161,412
Common Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			1,148
Stock based-awards			0
Repurchase of common shares			0
Dividends paid			0
Non-controlling interest additions			0
Amortization of deferred pension costs, net of tax			0
Interest rate swaps, net of tax			0
Net income			0
Ending balance	1,148		1,148
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			54,463
Stock based-awards			7,186
Repurchase of common shares			0
Dividends paid			0
Non-controlling interest additions			0
Amortization of deferred pension costs, net of tax			0
Interest rate swaps, net of tax			0
Net income			0
Ending balance	61,649		61,649
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			173,855
Stock based-awards			0
Repurchase of common shares			0
Dividends paid			(72,929)
Non-controlling interest additions			0
Amortization of deferred pension costs, net of tax			0
Interest rate swaps, net of tax			0
Net income			70,691
Ending balance	171,617		171,617
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(8,353)
Stock based-awards			0
Repurchase of common shares			0
Dividends paid			0
Non-controlling interest additions			0
Amortization of deferred pension costs, net of tax			145
Interest rate swaps, net of tax			931
Net income			0
Ending balance	(7,277)		(7,277)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(76,269)
Stock based-awards			11,347
Repurchase of common shares			(4,777)
Dividends paid			0
Non-controlling interest additions			0
Amortization of deferred pension costs, net of tax			0
Interest rate swaps, net of tax			0
Net income			0
Ending balance	(69,699)		(69,699)
Non-Controlling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			3,888
Stock based-awards			0
Repurchase of common shares			0
Dividends paid			0
Non-controlling interest additions			(10)
Amortization of deferred pension costs, net of tax			0
Interest rate swaps, net of tax			0
Net income			96
Ending balance	$ 3,974		$ 3,974