Fair Value Measurements and Derivative Instruments (Schedule of Impairment and Recovery of Previously Recorded Impairment) (Details) $ in Thousands	3 Months Ended					12 Months Ended
	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) property	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($) item
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impairment (loss) recovery, Total net impairments	$ 93	$ (553)	$ (848)	$ (479)	$ (271)	$ 93	$ (2,151)	$ (1,477)
Sold [Member] | Continuing Operations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of hotels						1	5	5
Impairment (loss) recovery, Total net impairments						$ 93	$ (2,151)	$ (1,477)
Sold [Member] | Continuing Operations [Member] | Impairment Loss [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of hotels | item							3	5
Impairment (loss) recovery, Sold hotels							$ (2,231)	$ (1,477)
Sold [Member] | Continuing Operations [Member] | Impairment Recovery [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of hotels						1	2
Impairment (loss) recovery, Sold hotels						$ 93	$ 80