Summary of Significant Accounting Policies - Deferred Charges, Segment Information and Shareholder Activism Costs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) segment area	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Information:
Number of business segments | segment	1
Number of geographic areas in which the Company operates | area	1
Costs related to shareholder activism | $	$ 0	$ 19,369	$ 0
Minimum
Deferred Charges:
Deferred lease costs, amortization period (in years)	1 year
Deferred financing costs, amortization period (in years)	1 year
Maximum
Deferred Charges:
Deferred lease costs, amortization period (in years)	15 years
Deferred financing costs, amortization period (in years)	15 years