Equity and Capital - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			$ 30,903
Accumulated Other Comprehensive Income Loss [Roll Forward]
Current period other comprehensive income, net	$ 11,524	$ 2,620
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			(14)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	9,003	(88)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,262)	(18,327)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2,157	2,610
Current period other comprehensive income, net	11,160	2,522
Ending balance	4,884	(15,805)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(119)	32
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(27)	(19)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Current period other comprehensive income, net	(119)	32
Ending balance	(146)	13
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			(14)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	8,884	(56)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,289)	(18,346)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2,157	2,610
Current period other comprehensive income, net	11,041	2,554
Ending balance	4,738	(15,792)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	502	21
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(112)	(301)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(19)	44
Current period other comprehensive income, net	483	65
Ending balance	371	(236)
Accumulated Net Investment Gain (Loss) Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Current period other comprehensive income, net	0	0
Ending balance	0	0
AOCI Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	502	21
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(112)	(301)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(19)	44
Current period other comprehensive income, net	483	65
Ending balance	371	(236)
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			$ (14)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	9,386	(35)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,401)	(18,647)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2,138	2,654
Current period other comprehensive income, net	11,524	2,619
Ending balance	5,109	(16,028)
Partnership Interest [Member]
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,289)
Current period other comprehensive income, net	11,524	$ 2,618
Ending balance	4,764
Accounting Standards Update 2017-12 [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,276)
Accounting Standards Update 2017-12 [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(27)
Accounting Standards Update 2017-12 [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,303)
Accounting Standards Update 2017-12 [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(112)
Accounting Standards Update 2017-12 [Member] | Accumulated Net Investment Gain (Loss) Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	0
Accounting Standards Update 2017-12 [Member] | AOCI Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(112)
Accounting Standards Update 2017-12 [Member] | AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	$ (6,415)