Accumulated Other Comprehensive Income - Summary of Changes in Accumulated Other Comprehensive Income (Loss) by Component (Parenthetical) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	$ 6,449,000	$ 10,977,000	$ 1,070,000
Unconsolidated Joint Ventures [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)	$ 0	$ 0	$ 0