Equity and Capital - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 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	$ 15,731	$ (3,768)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,262)	(18,327)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	4,663	7,922
Current period other comprehensive income, net	20,394	4,154
Ending balance	14,144	(14,173)
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	(51)	51
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	(51)	51
Ending balance	(78)	32
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	15,680	(3,717)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,289)	(18,346)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	4,663	7,922
Current period other comprehensive income, net	20,343	4,205
Ending balance	14,066	(14,141)
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	780	(143)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(112)	(301)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	38	132
Current period other comprehensive income, net	818	(11)
Ending balance	708	(312)
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	780	(143)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(112)	(301)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	38	132
Current period other comprehensive income, net	818	(11)
Ending balance	708	(312)
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	16,460	(3,860)
Accumulated Other Comprehensive Income Loss [Roll Forward]
Beginning balance	(6,401)	(18,647)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	4,701	8,054
Current period other comprehensive income, net	21,161	4,194
Ending balance	14,774	$ (14,453)
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)