Stockholders' Deficit - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands										12 Months Ended
	Feb. 20, 2020	Oct. 08, 2019	Aug. 01, 2019	May 13, 2019	Feb. 20, 2019	Oct. 06, 2018	Aug. 02, 2018	May 14, 2018	Feb. 14, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 01, 2015
Class of Stock [Line Items]
Authorized amount					$ 200,000
Dividends declared per common share (in dollars per share)	$ 0.76	$ 0.69	$ 0.69	$ 0.69	$ 0.69	$ 0.63	$ 0.63	$ 0.63	$ 0.63	$ 0.76	$ 2.76	$ 2.52
Reissuance of treasury stock (in shares)										433,477	285,302	167,396
Reissuance of treasury stock										$ 20,522	$ 11,969	$ 3,928
Treasury Stock
Class of Stock [Line Items]
Reissuance of treasury stock (in shares)										433,000	285,000	167,000
Reissuance of treasury stock										$ 19,420	$ 12,490	$ 6,479
2015 Authorization
Class of Stock [Line Items]
Authorized amount													$ 150,000