Related Party Transactions - Schedule of Asset Purchase and Asset Exchange Transactions for the Acquisition and Exchange of Expansion Territories and Facilities (Detail) - CCR [Member]		12 Months Ended
		Dec. 31, 2017	Jan. 01, 2017	Jan. 03, 2016	Dec. 28, 2014
Johnson City and Morristown Tennessee [Member]
Business Acquisition [Line Items]
Definitive Agreement Date					May 07, 2014
Acquisition / Exchange Date					May 23, 2014
Knoxville, Tennessee [Member]
Business Acquisition [Line Items]
Definitive Agreement Date					Aug. 28, 2014
Acquisition / Exchange Date					Oct. 24, 2014
Cleveland and Cookeville Tennessee [Member]
Business Acquisition [Line Items]
Definitive Agreement Date					Dec. 05, 2014
Acquisition / Exchange Date				Jan. 30, 2015
Louisville, Kentucky and Evansville, Indiana [Member]
Business Acquisition [Line Items]
Definitive Agreement Date					Dec. 17, 2014
Acquisition / Exchange Date				Feb. 27, 2015
Paducah and Pikeville, Kentucky [Member]
Business Acquisition [Line Items]
Definitive Agreement Date				Feb. 13, 2015
Acquisition / Exchange Date				May 01, 2015
Lexington, Kentucky for Jackson, Tennessee Exchange [Member]
Business Acquisition [Line Items]
Acquisition / Exchange Date				May 01, 2015
Norfolk, Fredericksburg and Staunton, Virginia and Elizabeth City, North Carolina [Member]
Business Acquisition [Line Items]
Definitive Agreement Date				Sep. 23, 2015
Acquisition / Exchange Date				Oct. 30, 2015
Easton and Salisbury, Maryland and Richmond and Yorktown, Virginia [Member]
Business Acquisition [Line Items]
Definitive Agreement Date				Sep. 23, 2015
Acquisition / Exchange Date			Jan. 29, 2016
Alexandria, Virginia and Capitol Heights and La Plata, Maryland [Member]
Business Acquisition [Line Items]
Definitive Agreement Date				Sep. 23, 2015
Acquisition / Exchange Date			Apr. 01, 2016
Baltimore Hagerstown and Cumberland, Maryland [Member]
Business Acquisition [Line Items]
Definitive Agreement Date				Sep. 23, 2015
Acquisition / Exchange Date			Apr. 29, 2016
Cincinnati, Dayton, Lima and Portsmouth, Ohio and Louisa, Kentucky [Member]
Business Acquisition [Line Items]
Definitive Agreement Date	[1]		Sep. 01, 2016
Acquisition / Exchange Date			Oct. 28, 2016
Anderson Fort Wayne Lafayette South Bend And Terre Haute Indiana Acquisitions [Member]
Business Acquisition [Line Items]
Definitive Agreement Date			Sep. 01, 2016
Acquisition / Exchange Date		Jan. 27, 2017
Sandston, Virginia [Member]
Business Acquisition [Line Items]
Definitive Agreement Date				Oct. 30, 2015
Acquisition / Exchange Date			Jan. 29, 2016
Indianapolis and Bloomington, Indiana and Columbus and Mansfield, Ohio [Member]
Business Acquisition [Line Items]
Definitive Agreement Date			Sep. 01, 2016
Acquisition / Exchange Date		Mar. 31, 2017
Silver Spring and Baltimore, Maryland [Member]
Business Acquisition [Line Items]
Definitive Agreement Date				Oct. 30, 2015
Acquisition / Exchange Date			Apr. 29, 2016
Akron, Elyria, Toledo, Willoughby and Youngstown, Ohio [Member]
Business Acquisition [Line Items]
Definitive Agreement Date		Apr. 13, 2017
Acquisition / Exchange Date		Apr. 28, 2017
Cincinnati, Ohio [Member]
Business Acquisition [Line Items]
Definitive Agreement Date			Sep. 01, 2016
Acquisition / Exchange Date			Oct. 28, 2016
Memphis, Tennessee [Member]
Business Acquisition [Line Items]
Definitive Agreement Date		Sep. 29, 2017
Acquisition / Exchange Date		Oct. 02, 2017
Little Rock and West Memphis, Arkansas for Leroy, Mobile and Robertsdale, Alabama, Panama City, Florida, Bainbridge, Columbus and Sylvester, Georgia, Ocean Springs, Mississippi and Somerset, Kentucky Exchange Transaction [Member]
Business Acquisition [Line Items]
Definitive Agreement Date		Sep. 29, 2017
Acquisition / Exchange Date		Oct. 02, 2017
Annapolis, Maryland Make-Ready Center [Member]
Business Acquisition [Line Items]
Definitive Agreement Date				Oct. 30, 2015
Acquisition / Exchange Date				Oct. 30, 2015
Indianapolis and Portland, Indiana [Member]
Business Acquisition [Line Items]
Definitive Agreement Date			Sep. 01, 2016
Acquisition / Exchange Date		Mar. 31, 2017
Expansion Facilities Twinsburg, Ohio [Member]
Business Acquisition [Line Items]
Definitive Agreement Date		Apr. 13, 2017
Acquisition / Exchange Date		Apr. 28, 2017
Memphis, Tennessee and West Memphis, Arkansas for Mobile, Alabama Exchange Transaction [Member]
Business Acquisition [Line Items]
Definitive Agreement Date		Sep. 29, 2017
Acquisition / Exchange Date		Oct. 02, 2017

[1] As amended by Amendment No. 1, dated January 27, 2017.