Consolidated Statements of Changes in Equity Statement (USD $)	Total	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Non-controlling Interest [Member]	Class A Common Stock [Member] Common Stock [Member]	Class B Common Stock [Member] Common Stock [Member]	Conversion Class B Common Stock to Class A Common Stock [Member]	Conversion Class B Common Stock to Class A Common Stock [Member] Additional Paid-in Capital [Member]	Conversion Class B Common Stock to Class A Common Stock [Member] Retained Earnings [Member]	Conversion Class B Common Stock to Class A Common Stock [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Conversion Class B Common Stock to Class A Common Stock [Member] Treasury Stock [Member]	Conversion Class B Common Stock to Class A Common Stock [Member] Non-controlling Interest [Member]	Conversion Class B Common Stock to Class A Common Stock [Member] Class A Common Stock [Member] Common Stock [Member]	Conversion Class B Common Stock to Class A Common Stock [Member] Class B Common Stock [Member] Common Stock [Member]	Conversion of Series A-1 Preferred Stock to Class A Common Stock [Member]	Conversion of Series A-1 Preferred Stock to Class A Common Stock [Member] Additional Paid-in Capital [Member]	Conversion of Series A-1 Preferred Stock to Class A Common Stock [Member] Retained Earnings [Member]	Conversion of Series A-1 Preferred Stock to Class A Common Stock [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Conversion of Series A-1 Preferred Stock to Class A Common Stock [Member] Treasury Stock [Member]	Conversion of Series A-1 Preferred Stock to Class A Common Stock [Member] Non-controlling Interest [Member]	Conversion of Series A-1 Preferred Stock to Class A Common Stock [Member] Class A Common Stock [Member] Common Stock [Member]	Conversion of Series A-1 Preferred Stock to Class A Common Stock [Member] Class B Common Stock [Member] Common Stock [Member]	RailAmerica [Member]	RailAmerica [Member] Additional Paid-in Capital [Member]	RailAmerica [Member] Retained Earnings [Member]	RailAmerica [Member] Accumulated Other Comprehensive Income (Loss) [Member]	RailAmerica [Member] Treasury Stock [Member]	RailAmerica [Member] Non-controlling Interest [Member]	RailAmerica [Member] Class A Common Stock [Member] Common Stock [Member]	RailAmerica [Member] Class B Common Stock [Member] Common Stock [Member]
BALANCE, at Dec. 31, 2011	$ 960,634,000	$ 385,473,000	$ 741,669,000	$ 37,895,000	$ (204,952,000)	$ 0	$ 527,000	$ 22,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	52,433,000	0	52,433,000	0	0	0	0	0
Other comprehensive income/(loss)	9,376,000	0	0	9,376,000	0	0	0	0
Dividends paid on Series A-1 Preferred Stock	(4,375,000)	0	(4,375,000)	0	0	0	0	0
Value of stock issued for stock-based compensation	19,320,000	19,311,000	0	0	0	0	9,000	0
Value of stock issued - Class A Common Stock	234,340,000	234,302,000	0	0	0	0	38,000	0
Value of TEU Purchase Contracts issued	191,428,000	191,428,000	0	0	0	0	0	0
RailAmerica acquisition consideration for stock-based awards	15,400,000	15,400,000	0	0	0	0	0	0
Conversion of Shares to Class A Common Stock									0	0	0	0	0	0	5,000	(5,000)
Compensation costs related to stock-based compensation included in income from equity investment in RailAmerica	2,816,000	2,816,000	0	0	0	0	0	0
Compensation cost related to stock-based compensation	12,151,000	12,151,000	0	0	0	0	0	0
Settlement of deferred stock awards	933,000	933,000	0	0	0	0	0	0
Excess tax benefits from stock-based compensation	4,795,000	4,795,000	0	0	0	0	0	0
Value of treasury stock repurchased	(4,314,000)	0	0	0	(4,314,000)	0	0	0
Noncontrolling interest - increase from RailAmerica acquisition																									5,525,000	0	0	0	0	5,525,000	0	0
BALANCE, at Dec. 31, 2012	1,500,462,000	866,609,000	789,727,000	47,271,000	(209,266,000)	5,525,000	579,000	17,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	272,091,000	0	271,296,000	0	0	795,000	0	0
Other comprehensive income/(loss)	(41,182,000)	0	0	(41,182,000)	0	0	0	0
Dividends paid on Series A-1 Preferred Stock	(2,139,000)	0	(2,139,000)	0	0	0	0	0
Value of stock issued for stock-based compensation	12,510,000	12,504,000	0	0	0	0	6,000	0
Conversion of Shares to Class A Common Stock									0	0	0	0	0	0	1,000	(1,000)	399,389,000	399,329,000	0	0	0	0	60,000	0
Compensation cost related to stock-based compensation	16,951,000	16,951,000	0	0	0	0	0	0
Settlement of deferred stock awards	274,000	274,000	0	0	0	0	0	0
Excess tax benefits from stock-based compensation	6,854,000	6,854,000	0	0	0	0	0	0
Value of treasury stock repurchased	(11,095,000)	0	0	0	(11,095,000)	0	0	0
Noncontrolling interest, change in fair value																									(5,045,000)	0	0	0	0	(5,045,000)	0	0
BALANCE, at Dec. 31, 2013	2,149,070,000	1,302,521,000	1,058,884,000	6,089,000	(220,361,000)	1,275,000	646,000	16,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	261,006,000	0	260,755,000	0	0	251,000	0	0
Other comprehensive income/(loss)	(78,341,000)	0	0	(78,341,000)	0	0	0	0
Value of stock issued for stock-based compensation	11,819,000	11,815,000	0	0	0	0	4,000	0
Conversion of Shares to Class A Common Stock									0	0	0	0	0	0	6,000	(6,000)
Compensation cost related to stock-based compensation	12,819,000	12,819,000	0	0	0	0	0	0
Excess tax benefits from stock-based compensation	6,198,000	6,198,000	0	0	0	0	0	0
Value of treasury stock repurchased	(4,186,000)	0	0	0	(4,186,000)	0	0	0
Cash distribution to non-controlling interest	(405,000)	0	0	0	0	(405,000)	0	0
BALANCE, at Dec. 31, 2014	$ 2,357,980,000	$ 1,333,353,000	$ 1,319,639,000	$ (72,252,000)	$ (224,547,000)	$ 1,121,000	$ 656,000	$ 10,000