LONG-TERM DEBT (Details) (USD $)	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
REVOLVING CREDIT FACILITY
Revolving credit facility	$ 426,000,000	$ 286,000,000
Senior unsecured notes	300,000,000	300,000,000
Total long-term debt	726,000,000	586,000,000
Revolving credit facility | Summit Holdings
REVOLVING CREDIT FACILITY
Variable rate basis	LIBOR
Weighted-average interest rate (as a percent)	2.40%	2.42%
Unused portion under the facility	$ 274,000,000
Commitment fee on unused portion of the facility (as a percent)	0.375%
Revolving credit facility | LIBOR | Summit Holdings
REVOLVING CREDIT FACILITY
Applicable margin (as a percent)	2.25%