Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Assets, Fair Value Disclosure, Nonrecurring, Period Increase (Decrease)	$ 0	$ 0
Liabilities, Fair Value Disclosure, Nonrecurring, Period Increase (Decrease)	$ 0	$ 0

Liabilities, Fair Value Disclosure, Nonrecurring, Period Increase (Decrease)

No definition available.

Name:	se_LiabilitiesFairValueDisclosureNonrecurringPeriodIncreaseDecrease
Namespace Prefix:	se_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration