Shareholders' Equity, Noncontrolling Interests and Other Comprehensive Income - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			$ 2,215,639	$ 2,178,125
Other comprehensive income before reclassifications			8,603	(2,008)
Reclassification of realized interest on swap agreements			472	1,903
Net current period other comprehensive loss	$ 3,059	$ (1,194)	9,075	(105)
Ending Balance	2,112,549	2,180,397	2,112,549	2,180,397
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			2,614	(798)
Ending Balance	$ 10,138	$ (520)	10,138	(520)
AOCI Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net current period other comprehensive loss			$ (1,551)	$ 383

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

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