Debt Obligations - Information on Borrowings under Current and Prior Credit Facility and Applicable Interest Rates (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Line of Credit Facility [Abstract]
Maximum amount outstanding during the period	$ 518,607	$ 123,768
Average daily amount outstanding under the credit facility	$ 472,029	$ 92,351
Weighted-average interest rate	2.00%	2.24%

Maximum amount borrowed under the credit facility at any time during the period.

No definition available.

Name:	us-gaap_LineOfCreditFacilityMaximumAmountOutstandingDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration