Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Stock Issued During Period, Shares, New Issues			1,475,000
Shares Issued During Period, Shares, New Issues, Price per Share			$ 116.67
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ (23,699)
Stock based-awards			16,762
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			(187)
Repurchase of common shares			(3,962)
Stock Issued During Period, Value, New Issues			197,202
Dividends paid			(70,883)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(211)
Cancellation of treasury shares			0
Amortization of deferred pension costs, net of tax			290
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ 256	$ (774)	(1,005)	$ (324)
Net income	16,838	$ 33,594	48,490	$ 99,338
Ending balance	$ 162,797		$ 162,797
Stock issued during period, Shares, New Issues, Additional Offering			221,250
Stock Issued During Period, Shares, New Issues, Net Proceeds			$ 197,200
Shares Outstanding [Member]
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			62,920
Shares, Outstanding	44,100,116		44,100,116		42,375,905
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			$ 0
Stock Repurchased During Period, Shares			(34,959)
Stock Issued During Period, Shares, New Issues			1,696,250
Dividends paid			$ 0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			0
Cancellation of treasury shares			0
Amortization of deferred pension costs, net of tax			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			0
Net income			0
Common Shares [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			1,142
Stock based-awards			0
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			0
Repurchase of common shares			0
Stock Issued During Period, Value, New Issues			38
Dividends paid			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			0
Cancellation of treasury shares			(32)
Amortization of deferred pension costs, net of tax			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			0
Net income			0
Ending balance	$ 1,148		1,148
Additional Paid-In Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			0
Stock based-awards			8,457
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			(187)
Repurchase of common shares			0
Stock Issued During Period, Value, New Issues			197,164
Dividends paid			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			0
Cancellation of treasury shares			(142,955)
Amortization of deferred pension costs, net of tax			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			0
Net income			0
Ending balance	62,479		62,479
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			219,207
Stock based-awards			0
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			0
Repurchase of common shares			0
Stock Issued During Period, Value, New Issues			0
Dividends paid			(70,883)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			0
Cancellation of treasury shares			0
Amortization of deferred pension costs, net of tax			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			0
Net income			48,436
Ending balance	196,760		196,760
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(10,538)
Stock based-awards			0
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			0
Repurchase of common shares			0
Stock Issued During Period, Value, New Issues			0
Dividends paid			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			0
Cancellation of treasury shares			0
Amortization of deferred pension costs, net of tax			290
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			(1,005)
Net income			0
Ending balance	(11,253)		(11,253)
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(238,875)
Stock based-awards			8,305
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			0
Repurchase of common shares			(3,962)
Stock Issued During Period, Value, New Issues			0
Dividends paid			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			0
Cancellation of treasury shares			142,987
Amortization of deferred pension costs, net of tax			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			0
Net income			0
Ending balance	(91,545)		(91,545)
Non-Controlling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			5,365
Stock based-awards			0
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			0
Repurchase of common shares			0
Stock Issued During Period, Value, New Issues			0
Dividends paid			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(211)
Cancellation of treasury shares			0
Amortization of deferred pension costs, net of tax			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			0
Noncontrolling interest, net income			54
Ending balance	$ 5,208		$ 5,208