CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 152,146us-gaap_ProfitLoss	$ 44,640us-gaap_ProfitLoss	$ 89,936us-gaap_ProfitLoss
Other Comprehensive (loss) income:
Unrealized (loss) gain on valuation of swap agreements	(9,061)	3,610	(3,519)
Reclassification of realized interest on swap agreements	3,776	2,892	2,268
Other comprehensive (loss) income	(5,285)	6,502	(1,251)
Comprehensive income	146,861	51,142	88,685
Comprehensive income attributable to noncontrolling interests	(80,934)	(5,588)	(49,373)
Comprehensive income attributable to Common Shareholders	$ 65,927us-gaap_ComprehensiveIncomeNetOfTax	$ 45,554us-gaap_ComprehensiveIncomeNetOfTax	$ 39,312us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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