Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Investment interest income	$ 23,248	$ 34,963
Depreciation and amortization expense	19,017	12,042
Accrued interest receivable	53,586		51,640
Intangible assets, accumulated amortization	14,995		13,911
Intangible assets, amortization expenses	3,931		1,946
Expected amortization expense of intangible assets in 2015	5,950
Expected amortization expense of intangible assets in 2016	5,226
Expected amortization expense of intangible assets in 2017	3,785
Expected amortization expense of intangible assets in 2018	3,109
Expected amortization expense of intangible assets in 2019	2,934
Expected amortization expense of intangible assets thereafter	9,706
Goodwill	11,014		11,014
Customer relationships
Significant Accounting Policies [Line Items]
Intangible assets, gross carrying amount	19,149		19,149
In-place leases
Significant Accounting Policies [Line Items]
Intangible assets, gross carrying amount	25,056		22,725
Trade name
Significant Accounting Policies [Line Items]
Intangible assets, gross carrying amount	1,500		1,500
Loans and Finance Receivables
Significant Accounting Policies [Line Items]
Accrued interest receivable	42,536		41,347
Building and Building Improvements | Minimum
Significant Accounting Policies [Line Items]
Property, useful lives	30 years
Building and Building Improvements | Maximum
Significant Accounting Policies [Line Items]
Property, useful lives	40 years
Furniture, fixtures, and equipment | Minimum
Significant Accounting Policies [Line Items]
Property, useful lives	5 years
Furniture, fixtures, and equipment | Maximum
Significant Accounting Policies [Line Items]
Property, useful lives	10 years
Cash Flows from Operating Activities
Significant Accounting Policies [Line Items]
Increase (decrease) in cash flows activities		26,547
Cash Flows from Investing Activities
Significant Accounting Policies [Line Items]
Increase (decrease) in cash flows activities		(26,547)
Scenario, Adjustment
Significant Accounting Policies [Line Items]
Investment interest income	842
Depreciation and amortization expense	$ 708