Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2016

Fair Value [Abstract]

Carrying Values and Fair Values of Debt Instruments

The carrying values and fair values of the Company’s debt instruments where the carrying values do not approximate their fair values as of March 31, 2016 and December 31, 2015, are as follows: 

	Carrying Value at				Fair Value* at
	March 31, 2016		December 31, 2015		March 31, 2016		December 31, 2015
3.30% Senior Notes due 2016	$	100,000	$	100,000	$	100,006	$	100,536
4.00% Senior Notes due 2018	$	50,000	$	50,000	$	52,005	$	51,860
5.25% Senior Notes due 2019	$	175,000	$	175,000	$	193,070	$	190,985
4.64% Senior Notes due 2021	$	100,000	$	100,000	$	109,872	$	107,613
3.09% Senior Notes due 2022	$	125,000	$	125,000	$	127,477	$	123,516
3.41% Senior Notes due 2025	$	375,000	$	375,000	$	384,754	$	370,245

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*Senior Notes are classified as Level 2 within the fair value hierarchy.  Fair value is based on quotes of bonds with similar ratings in similar industries.