Equity and Capital - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
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			$ 12
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	$ 13,156	$ (3,770)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,262)	(18,327)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	3,513	5,638
Current period other comprehensive income, net	16,669	1,868
Ending balance	10,419	(16,459)
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	(75)	43
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	(75)	43
Ending balance	(102)	24
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			12
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	13,081	(3,727)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,289)	(18,346)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	3,513	5,638
Current period other comprehensive income, net	16,594	1,911
Ending balance	10,317	(16,435)
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			2
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	638	(103)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(112)	(301)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	40	88
Current period other comprehensive income, net	678	(15)
Ending balance	568	(316)
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			2
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	638	(103)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(112)	(301)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	40	88
Current period other comprehensive income, net	678	(15)
Ending balance	568	(316)
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	13,719	(3,830)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,401)	(18,647)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	3,553	5,726
Current period other comprehensive income, net	17,272	1,896
Ending balance	10,885	$ (16,751)
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	(6,250)
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	(6,277)
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	(110)
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	(110)
Accounting Standards Update 2017-12 [Member] | AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	$ (6,387)