Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 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			11,087
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			(284)
Repurchase of common shares			(1,112)
Stock Issued During Period, Value, New Issues			197,211
Dividends paid			(46,626)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(211)
Amortization of deferred pension costs, net of tax			194
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ (372)	$ 1,347	(1,261)	$ 450
Net income	16,535	$ 34,702	31,652	$ 65,744
Ending balance	$ 166,951		$ 166,951
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			33,892
Shares, Outstanding	44,095,883		44,095,883		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			(10,164)
Stock Issued During Period, Shares, New Issues			1,696,250
Dividends paid			$ 0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			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
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	$ 1,180		1,180
Additional Paid-In Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			0
Stock based-awards			6,488
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			(284)
Repurchase of common shares			0
Stock Issued During Period, Value, New Issues			197,173
Dividends paid			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			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
Ending balance	203,377		203,377
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			(46,626)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			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			31,706
Ending balance	204,287		204,287
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
Amortization of deferred pension costs, net of tax			194
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			(1,261)
Net income			0
Ending balance	(11,605)		(11,605)
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(238,875)
Stock based-awards			4,599
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation			0
Repurchase of common shares			(1,112)
Stock Issued During Period, Value, New Issues			0
Dividends paid			0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			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
Ending balance	(235,388)		(235,388)
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)
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	$ 5,100		$ 5,100