Related Party Transactions (Summarized Financial Information of Company's Equity Method Investees) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Sales and merchandising revenues	$ 812,662	$ 685,579	$ 911,402	$ 635,739	$ 1,004,072	$ 836,595	$ 993,662	$ 852,016	$ 3,045,382	$ 3,686,345	$ 3,924,790
Gross profit	93,962	$ 53,864	$ 90,474	$ 63,705	84,836	$ 69,671	$ 87,834	$ 76,458	302,005	318,799	345,506
Net income (loss)									41,225	42,609	14,470
Current assets	1,023,198				999,211				1,023,198	999,211
Current liabilities	833,350				738,716				833,350	738,716
Noncontrolling interests	876,764				822,899				876,764	822,899	790,697	$ 783,739
Subsidiaries
Related Party Transaction [Line Items]
Sales and merchandising revenues									6,111,036	6,080,795	6,579,413
Gross profit									257,594	217,629	188,350
Income from continuing operations									71,608	50,937	12,288
Net income (loss)									68,876	42,970	6,445
Current assets	1,111,826				1,045,124				1,111,826	1,045,124	898,081
Non-current assets	526,169				538,671				526,169	538,671	565,416
Current liabilities	792,184				802,161				792,184	802,161	665,387
Non-current liabilities	281,103				309,649				281,103	309,649	359,816
Noncontrolling interests	$ 0				$ 0				$ 0	$ 0	$ 3,628