Stockholders' Equity and Non-controlling Interests - Redeemable non-controlling interest in the Operating Partnership (Details) - USD ($)													3 Months Ended		12 Months Ended
	Mar. 27, 2017	Feb. 22, 2017	Nov. 03, 2016	Oct. 14, 2016	Aug. 03, 2016	Jul. 15, 2016	May 25, 2016	May 09, 2016	Apr. 15, 2016	Mar. 08, 2016	Mar. 02, 2016	Jan. 13, 2016	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Oct. 29, 2014
Change in redeemable non-controlling interest
Net income (loss) attributable to non-controlling interests														$ (101,000)
Redeemable non-controlling interests in operating partnership, preferred units													$ 117,877,000		$ 119,915,000
Cash dividend paid (in dollars per share)				$ 0.1275		$ 0.1275			$ 0.1275			$ 0.1275
Cash distributions (in dollars per share)		$ 0.1275	$ 0.1275		$ 0.1275			$ 0.1275		$ 0.1275			$ 0.1275	$ 0.1275	$ 0.5100
Share repurchase
Change in redeemable non-controlling interest
Stock repurchased													$ 0
Share repurchase | Maximum
Change in redeemable non-controlling interest
Amount approved for share repurchase program																$ 25,000,000
Redeemable OP units
Change in redeemable non-controlling interest
Distributions on redeemable non-controlling interests in operating partnership														$ (113,000)
Redeemable non-controlling interest, temporary equity dividends accrued														113,000
Redeemable Preferred OP Units
Change in redeemable non-controlling interest
Distributions on redeemable non-controlling interests in operating partnership													$ (878,000)	(283,000)
Percentage of cumulative preferential dividends													3.00%
Distributions payable													$ 878,000	283,000
Redeemable non-controlling interest, temporary equity dividends accrued													$ 878,000	283,000
Series A Preferred Units
Change in redeemable non-controlling interest
Percentage of preferential cash distribution											3.00%
Liquidation preference											$ 1,000
Number of trading days													20 days
Series A Preferred Units | Illinois | Asset acquisition
Stockholders’ Equity and Non-controlling Interests
Issuance of stock as consideration in real estate acquisition (in shares)											117,000
Change in redeemable non-controlling interest
Liquidation value													$ 117,877,500	117,283,000
OP units
Change in redeemable non-controlling interest
Stock repurchased (in shares)	129,174
OP units | Redeemable OP units
Stockholders’ Equity and Non-controlling Interests
Temporary Equity redeemable for cash							883,724
Change in redeemable non-controlling interest
Opening balance														$ 9,695,000	$ 9,695,000
Opening balance (in shares)														884,000	884,000
Net income (loss) attributable to non-controlling interests														$ (101,000)
Distributions on redeemable non-controlling interests in operating partnership														(113,000)
Adjustment to arrive at redemption value of redeemable non-controlling interests in Operating Partnership, common														38,000
Ending balance														$ 9,519,000
Ending balance (in shares)														884,000
Redeemable non-controlling interest, temporary equity dividends accrued														$ 113,000
OP units | Redeemable Preferred OP Units
Change in redeemable non-controlling interest
Opening balance													$ 119,915,000
Opening balance (in shares)													117,000
Issuance of redeemable OP units as partial consideration for real estate acquisition														$ 117,000,000
Issuance of redeemable OP units as partial consideration for real estate acquisition (in shares)														117,000
Distributions on redeemable non-controlling interests in operating partnership													$ 878,000	$ 283,000
Distributions paid to non-controlling interest													(2,915,000)
Redeemable non-controlling interests in operating partnership, preferred units													$ 117,878,000
Ending balance														$ 117,283,000	$ 119,915,000
Ending balance (in shares)													117,000	117,000	117,000
Redeemable non-controlling interest, temporary equity dividends accrued													$ (878,000)	$ (283,000)