Other Assets - Schedule of Investing Commitment (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Other Commitments [Line Items]
Original commitment amount	$ 37,566
Less: life to date contributions	(32,070)
Remaining commitment amount	$ 5,496
R4 - MVV
Other Commitments [Line Items]
Years over which tax credits are earned	17 years
Original commitment amount	$ 8,528
Less: life to date contributions	(8,248)
Remaining commitment amount	$ 280
R4 - Coronado
Other Commitments [Line Items]
Years over which tax credits are earned	17 years
Original commitment amount	$ 10,729
Less: life to date contributions	(10,138)
Remaining commitment amount	$ 591
R4 - PJ33
Other Commitments [Line Items]
Years over which tax credits are earned	17 years
Original commitment amount	$ 6,809
Less: life to date contributions	(2,184)
Remaining commitment amount	$ 4,625
WNC
Other Commitments [Line Items]
Years over which tax credits are earned	16 years
Original commitment amount	$ 2,500
Less: life to date contributions	(2,500)
Remaining commitment amount	$ 0
USA 57
Other Commitments [Line Items]
Years over which tax credits are earned	15 years
Original commitment amount	$ 3,000
Less: life to date contributions	(3,000)
Remaining commitment amount	$ 0
Centerline XXXIII
Other Commitments [Line Items]
Years over which tax credits are earned	18 years
Original commitment amount	$ 3,000
Less: life to date contributions	(3,000)
Remaining commitment amount	$ 0
Centerline XXII
Other Commitments [Line Items]
Years over which tax credits are earned	18 years
Original commitment amount	$ 3,000
Less: life to date contributions	(3,000)
Remaining commitment amount	$ 0